These would be the 1. logic tier, 2. the presentation tier, and 3. the data tier.Image via Wikimedia CommonsThe separate physical location of these tiers is what differentiates n-tier architecture from the model-view-controller framework that only separates presentation, logic, and data tiers in concept. Monolith and microservices refer to how an application is distributed (or not), while layered is one of the options available for the internal application's architecture. Just trying to write cleaner code each day | My story - https://youtu.be/Zr73KfbiSu0, // This will allow our presentation layer to retrieve data from this API without, // running into cross-origin issues (CORS), // ============================================, // ========== DATABASE CONNECTION ===========, // Define the mongoose model for use below in method, // ============ API ENDPOINT ================, // ============== SERVER =====================, , // Perform the GET request to the business layer, // ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^. Opinions expressed by DZone contributors are their own. Modifiability - if the developers want to add a feature to the system, is it easy to do? Furthermore, code from each layer is stored in a clearly marked folder (i.e. They apply to different aspects os software systems. Don't fall into the architecture astronaut trap. Deployability - is it easy to put a new feature in production? This hampers innovation as consuming teams are not aware of the actual potential inside another layer. Regarding the n layered architecture - it is ok, and all monolith, or microservices, should implement it these days anyway. When working on a Microservice Architecture, layers may appear in two different ways — one good, one not so good. If you are a financial services company, the most important quality attribute for your system would probably be security (a breach of security could cause your clients to lose millions of dollars) followed by availability (your clients need to always have access to their assets). This means you could host them on completely different servers and still make the application work. How am I supposed to architect a solution with little prior experience? There are so many architectures and design patterns. They think in patterns that allow them to minimize changing more than one layer, essentially pigeonholing the architecture into a single corner. Throughout this post, we'll work through these concerns and figure out what this architecture thing is all about. a user updated their home address; this home address needs to travel through several layers, unmodified, to the Persistence Layer to finally be stored in a database. Often large enterprises may have teams with directors and VPs that feel they own a specific business capability. Microservice Architecture Viraj Brian Wijesuriya vbw@ucsc.cmb.ac.lk 1 SCS 4120 - Software Engineering IV BACHELOR OF SCIENCE HONOURS IN COMPUTER SCIENCE BACHELOR OF SCIENCE HONOURS IN SOFTWARE ENGINEERING All in One Place Lecture Notes Distribution Among Friends Only All copyrights belong to their respective … It takes a touch of genius—and a lot of courage to move in the opposite direction". With you every step of your journey. For those of us (including myself) not so experienced in designing architecture, we must accept that things won't be perfect and design it anyway. This also allows multiple team members to work on the application at once. Similarly, developers at the Persistence Layer don't need to worry about how data is being displayed, how long text is handled, etc. Below are a few examples of quality attributes: Depending on what software you are building or improving, certain attributes may be more critical to success. If you are swimming (or drowning) in a microservice ocean you may see layers emerge. By separating these concerns teams can ensure consistency and focus on their specific work. Often different layers run on separate hardware and are individually protected ensuring only a specific neighboring layer has access. Microservice #1 - User Authentication (http://localhost:8081). Update (10/24/20): Thank you, Carlos G for pointing this out in the comments--When talking about these 3 architectures, they are not perfect comparisons. A hacker coming in through the UI Layer would have to hack multiple independent systems to finally penetrate to somewhere worth hacking into. If you are a gaming or video streaming company (i.e. Service-Oriented Architecture vs Microservices is now becoming the top priority for a significant group of developers as these architectures help them in developing applications that are independently deployable and consist of a set of dissociated services. Netflix), your first quality attribute is going to be performance because if your games/movies freeze up all the time, nobody will play/watch them. Build something that works and call it a day. As mentioned above, you may find it useful to start out with something like this and as the application grows, start refactoring the pieces into a more manageable architecture. When developing a server-side application you can start it with a modular hexagonal or layered architecture which consists of different types of components: 1. But with cloud computing and mobile devices, backend must be available at all times for a wide range of devices. The UI Layer can only talk to the layer directly below it (or in theory the layer directly above it). Instead, we are talking about API endpoints (i.e. The Persistence Layer would typically be closed to the world and only open to the Business Logic Layer and the database itself. Over a million developers have joined DZone. On the other hand, core business capabilities will not change overnight and architects may choose more robust enterprise type technology stacks like Oracle and Java. As the name suggests, this architectural style focuses on layering. Since each service takes care of one function of the software, reusing them while developing other systems is relatively easy. "Any intelligent fool can make things bigger, more complex, and more violent. Furthermore, the "layered" example below would more accurately be classified as a "properly written monolith". Microservices can be developed as a set of event-driven functions and stored on the third-party vendor’s infrastructure. Made with love and Ruby on Rails. IMO it is not fair, even accurate, to compare these three architectures. Presentation layer makes a call from an HTML user form, 2. My Monolith SJW spirit feels way more calm now :D. About the levels of quality you can find inside a monolith, I am experiencing right now the curious situation of how, in order to be able to extract some functionality out of a poorly designed monolith to some separate service, the process of decoupling and isolating the code is leading to some decent implementation of it and removing the need of a new service and all the burden it implies in terms of communication, testability, etc. He notes that those who start their applications as microservice architectures usually end up wasting time and energy because you don't start seeing the benefits of this architecture until the application becomes complex. In the code mentioned above, we have three parts to our microservices architecture: Notice how each of the servers run independently on different ports. microservices and SOA architecture patterns. This is made possible because the authentication microservice is decoupled from the underlying infrastructure with robust APIs. Don't fall into analysis paralysis. Technical and business capabilities and organizational structure - often these can be somewhat intertwined. For example, creating an effective peer-to-peer architecture (i.e. All other layers will remain as is and will not even have to be tested after the Persistence Layer has been thoroughly vetted. Presentation Layer folks may be highly skilled in Javascript and CSS and live confidently that nobody will ask them to performance tune a SQL query. The hypothetical application handles requests by executing business logic, accessing databases, and then returning HTML, JSON, or XML responses. Either way, teams will adjust and treat other team's business capabilities as black boxes and build abstractions around them. Additionally, each layer has its own access control. This sounds great, but there is one problem that this architecture does not solve. Monolithic vs. Microservices Architecture’s Tabular Comparison. You will see in the application that I have created a much much much much much (did I say much?) If it was on one of the last few editions it is likely that it is still relevant. To demonstrate, I will be using NodeJS, ExpressJS, and MongoDB in the context of a web application. Portability - can the system run on many different platforms (i.e. These microservices provide specialized, fine-grained cooperation that makes up the more comprehensive architecture model. These services are created to serve only one specific business function, such as User Management, User Roles, E-commerce Cart, Search Engine, Social Media Logins etc. One of the ways we can refactor is through the concept of a layered architecture. A monolithic architecture describes an architecture where all of the following components are bunched into one codebase: Although this architecture may seem ineffective, not all industry professionals believe it is useless. What if I choose the wrong one? Interoperability - does the system play nicely with other systems? I believe the easiest way to learn software architecture is to see it in practice. Data access layer returns the information to the business layer, 6. Business layer returns the information via HTTP to the presentation layer, 7. We're a place where coders share, stay up-to-date and grow their careers. The UI Layer, for example, would often be driven by security and usability concerns. Poor server processing time us delve into the benefits of building white label cryptocurrency software using microservices architecture … can be hosted on different servers, which you can't do with monolith. Layers can be good if you maintain them properly — they need strong governance. Microservices has become an increasingly popular service architecture, but it’s essential to understand whether it’s the best fit for your project. As you become more experienced, you may begin to see the usefulness of other architectural patterns. Presentation layer javascript processes the form and executes a call to the business layer, 3. Business layer processes the form info and makes a call to the data access layer, 4. At the bottom layer, we have fine-grained self-contained services (no external service dependencies) that mostly comprise of the business logic and less or no network communication logic. Microservices architecture. For example, when a user enters information into the register form and clicks the register button, the following function is triggered, and a POST request is sent to the /register endpoint. This maybe good - they want to ensure reliability to many clients that rely on their services, or bad - they simply want to push their weight around and stay relevant. The critical factor in a layered architecture is the rule that each layer can only utilize the layer directly below it. Layering Microservices. Microservices Architecture vs. SOA As discussed above, ... You may be sitting on an n-tier Layered architecture deadly microservices antipatterns, such as search Z-axis! Organizations design systems that reflect the communication structure of the organization. Data access layer processes the information and makes a query to the database for the user, 5. How can I create an entire architecture without knowing all the details about the code I'm going to write? My examples below are not meant to demonstrate the proper way to code an application, but rather to explicitly call out the various architectures that you can use within your codebase. If for some reason, this didn't work, debugging will be challenging as we have to follow the data through several layers. Layered architectures introduce technological independence but inadvertently end up creating logical coupling across distributed environments. Developers may find that they don't want to edit the UI Layer and the Aggregation Layer as that may require testing and debugging of two layers including the network connection between them. DEV Community – A constructive and inclusive social network for software developers. Usually, the layering is driven by two factors. It provides some cohesion in terms of team capabilities and clarities in terms of responsibilities. From E.F. Schumacher's book Small is Beautiful, this quote embodies a lot of what architecting software means. "Monolith" has some undeserved bad press I trend to counter when possible ;). But why do we need an architecture to do this? Security - does the system have a secure fortress around it? This worked well in the age of mainframes and desktops. This is the goal of microservices. Likewise, just because you have a microservices architecture in place does not ensure that you have a perfectly "layered" codebase within it. Sep 24, 2018 • Architecture • Microservices • Meetup • Patterns • Edge • Distributed Systems • At Meetup, we are going through the oh-so-familiar path of splitting a monolithic system into microservices. A perfect example is Google because you not only use your login credentials for Gmail and other core Google services; you also use it to log into YouTube and many other applications. A UI Layer may capture a profile change, e.g. simpler authentication microservice than what Google owns. Often these layers also match the business functions of teams. 1. Let's take a look at the internals of a simple monolithic architecture. According to the book Software Architecture in Practice, there are 13 reasons why Software Architecture is important for the success of a project. Here’s how development teams can approach building a combined system without choosing between microservices architecture vs serverless architecture. And finally, to your point on monolithic architectures getting bad press, I definitely agree. The main thing that you will see with this code is a lack of distinction between application parts. They can see much further into the future and anticipate how certain design decisions will impact the system. As you point out in your post, the simplest choice that covers your quality needs is the way to go. This is a good thing and an aspect of evolutionary architecture. This is where an experienced architect has an advantage over a novice. But, before start this topic, I want to shed some light on the Layered Architecture. Therefore, it is critical to not only implement the user functionality but maintain proper security and protect the users' data. See the original article here. Each piece of the application communicates through HTTP protocol and therefore can operate independently. There is another click listener on the buttons that start and stop the game. In this case, you could create an additional layer that is considered "open" for all layers to use. Microservices architecture increases operational complexity but is flexible in its design to enable continuous integration and delivery of n… Templates let you quickly answer FAQs or store snippets for re-use. When the game is stopped, the following function is triggered, and a POST request is sent to the /score endpoint: Finally, when you click the button to see your scores, the following function is invoked, and a GET request is sent to the /score/:email endpoint. Teams in the same organization end up having to innovate in isolation. Microservice and layered architecture are a little bit different things. The microservices architecture style naturally evolved from two main sources: monolithic applications developed using the layered architecture pattern and distributed applications developed through the service-oriented architecture pattern. To be serverless, microservices should be event-triggered. Imagine if Google implemented a user authentication scheme in each individual application!! Microservice Architecture describes an approach where an application is developed using a collection of loosely coupled services. Join the DZone community and get the full member experience. They have both similarities and differences; here, we are going to understand their concepts and their differences. business-layer). He suggests starting with a monolithic architecture and refactoring it later into a layered or microservice architecture when it becomes too large to handle all in one piece. A digital design team, or even a third party agency, may be maintaining the UI layer. Built on Forem — the open source software that powers DEV and other inclusive communities. In many complex applications, an entire server will be devoted to authenticating and managing users. The game microservice is a bit simpler than the user authentication microservice but demonstrates how we can separate core pieces of functionality of our applications. You can have a microservices architecture that utilizes a layered architecture within each microservice. Also, the microservices and all of it's services, frontend apps etc. We strive for transparency and don't collect excess data. As the name implies, a microservices architecture is an approach to building a server application as a set of small services. the communication between the microservices). Teams can become focused and achieve mastery at the layer that they are developing and maintaining. Microservices architecture provides much more reusable components in the form of services. wanted to build an instant messaging system or chat application, you might look towards and Event-Driven Architecture. If you want to make any large changes to a single layer, you will have to re-deploy the entire application to implement the changes. Although many modern architects will turn to a microservices design to solve this problem (covered in the next section), another option to better segregate the duties of the application is to refactor your monolith. 09/20/2018; 3 minutes to read; n; j; m; In this article. Over time a distinct separation will appear and it would be advisable to introduce a gateway between the two to further ensure independence. Unfortunately, as a developer and architect, you get no additional bonus points for indirectly solving problems. It should a… The user cares that your system is fast, reliable, and available, The project manager cares that the system is delivered on time and on budget, The CEO cares that the system contributes incremental value to his/her company, The head of security cares that the system is protected from malicious attacks, The application support team cares that the system is easy to understand and debug. The intention in the post was to highlight the difference between having files that circularly referenced each other (i.e. You have certainly seen different architectures while reading through codebases, but you probably haven't recognized them. If developers want to updat… Previously, applications were based on centralized multi-tier architecture. If you have ever taken tutorials online that teach you how to build a web application, you have most likely built a monolithic application. Therefore, when designing software architecture, you must decide which quality attributes matter most for the given business problem. Developer This microservice is solely responsible for managing gameplay results of all the application users registered through the authentication microservice. For example, Martin Fowler advocates for the use of monolithic architectures when starting a new application. Note: The password authentication is not implemented as you should in a production application; it is solely for demonstration and you should never store your users' passwords in plain text like I am doing here! From my experience, I would say that anything you are designing from scratch (i.e. I do agree with you when you say "how an app is distributed" in that monolithic does not necessarily mean disorganized and poor coding patterns, and I realize that this post does not highlight that fact well. I haven't seen the video, maybe there you go more in details on it, but considered worth to comment the above. You can see that the url property is set to our User Authentication microservice. Although there are no strict rules on how you must build your microservices, it is common to utilize something like a layered architecture to structure them. That means a microservices architecture is mainly oriented to the back-end, although the approach is also being used for the front end. Bitcoin, Bittorrent) is no easy undertaking. Any change within any of the intervening layers may have triggered the address to be lost. This centralization we see is not sustainable into the future, but that doesn't mean it is all bad. Here’s how development teams can approach building a combined system without choosing between microservices architecture vs serverless architecture. Usually, you will find the following layers (in order): You may also stumble upon alternate terminology: No matter what you call the layers, the point is to create a "separation of concerns" where each layer is only allowed to use the layer directly below it. "Service-oriented architecture composed of loosely coupled elements that have bounded contexts" by Adrian Cockcroft (Amazon) "Conway's Law states that Organizations that design systems are constrained to produce copies of the communication structures of these organizations [...] the organization chart will initially reflect the first system design, which is almost surely not the right one [...] as one learns, he changes the design [...]. Microservices can be developed as a set of event-driven functions and stored on the third-party vendor’s infrastructure. Security is heightened by a Layered Architecture. There’s no need to scale … 2. Business logic — the application’s business logic. It is unified and all the functions are managed and served in one place.Normally, monolithic applications have one large code base and lack modularity. What emerges is a Layered Architecture of sets of Microservices consisting of specific team's business capabilities. You will learn the basics of each of these architectures and core differences between them in terms of the architecture style, architecture characteristics, service characteristics, and capabilities. We will say that the application must support a variety of clients, including desktop browsers running Single Page Applications (SPAs), traditional web apps, mobile web apps, and native mobile apps. It is by far the easiest to conceptualize starting out. In the sample app linked above, I have created a basic User Authentication flow that illustrates this concept. It's about delivering a system that works effectively. N-tier architecture also differs from MVC framework in t… Database access — data access objects responsible for access the database. Enterprise architects get paid lots of money because architecting a quality software is difficult and requires experience. Whatever your situation, there is an architecture out there for you. This post defines microservices architecture and outlines some best practices for designing one. If you were trying to build Bitcoin, you might look at a peer-to-peer architecture. As we walk through the pieces of this application, notice how we are not talking about "call chains" anymore. Presentation layer renders the view with the new information. However, microservices are too granular when it comes to architecting larger systems and projects in the brownfield. So as you think about architectures, just remember that an application (or microservice) can have several "architectures". business capabilities and organizational structure - often these can be somewhat intertwined You could even add some event-driven architecture if you wanted. Availability - what percentage of the time is the system running? You can end up with crappy code, like the one used as example for the monolith application, while building microservices. Developers working on the UI Layer don't need to worry about privacy or data security as the Persistence Layer will ensure that data stored is secured, potentially encrypted, and that data access is controlled. For example, if you were trying to build a platform like Wordpress that has a core system which can be extended via plugins, you might opt for a microkernel architecture. An Engagement Layer may be separate from a Business Capabilities Layer. – eja May 4 '19 at 16:42 In some cases, you may have a shared layer that has utility functions. In this blog post, we’ll explore the evolution of development from monolithic architectures toward microservices and its underlying justifications, as well as the pros and cons of microservices. Nevertheless, it demonstrates how we might implement an "authentication API" for one or more applications. Microservice architecture it’s about how your application is constructed, what components (services) it has and how these services communicate with each other, how they are developed, deployed and so on. As we walked through each of the steps, you may have noticed how each layer is responsible for a very specific duty. To be serverless, microservices should be event-triggered. Safety - if the software controls physical things, is it a hazard to real people? You could have one team implementing all of the database calls in the data layer, another team implementing the REST API in the business layer, and another team creating the front-end user interface! Application/Business Logic (i.e. Even if we wanted to modify an API call in home.ejs, we would probably need to make changes to app.js. All code mentioned below is stored in my microservices architecture repository on Github. After all, without users, you have no application. It solves the "release schedule" problem and allows developers to independently engineer each piece of a larger application. Adopting Microservices at Netflix: Lessons for Team and Process Design discusses why and how to adopt a new mindset for software development and reorganize your teams around it. And layered vs microservices architecture about architectures, there is one problem that this architecture thing is all.. N'T leave the layers porous front end or mobile applications as suites independent! The steps with code now n't try to think about architectures, just that!, like the one used as example for the given business problem the user functionality but maintain security!, I would say that anything you are designing from scratch ( i.e I to. Choose from but rigid in its design to support continuous delivery of new capabilities of small services,. Architecture within each microservice different servers and still make the real money by solving complex... In terms of responsibilities and more violent as black boxes and build abstractions around.. Factor in a microservice ocean you may have teams with directors and VPs feel! Want to shed some light on the other hand, the microservices that need to edit.... In apps can be hosted on different servers, which you ca n't do with monolith or microservices should... Api calls when certain events happen has an advantage over a novice fit desired... Beautiful, this may not always happen as organizations may get sloppy and be weak with the security of communication. Like I originally did -- mutually exclusive used as example for the success of a layered is., layered, and a database something that works effectively and MongoDB in the application at once this course the! Architecture of sets of microservices consisting of specific team 's business capabilities this concept architects and may... Of the system run on many different ways — one good, not. To app.js monolithic application with a `` Poorly designed monolith '' easily figure out the interface of the software physical. Approach where an application is developed using a collection of loosely coupled services below it ( or microservice can... An approach to layered vs microservices architecture a combined system without choosing between microservices architecture serverless! That feature creep does n't mean it has a poor `` layered '' approach.. The code linked above is the presence of a desirable project application built! Each microservice at once three architectures structured in many different ways — one,... Community and get the full member experience independently engineer each piece of a project, it a! Many layers consisting of specific team 's business capabilities layer highlight the difference between files..., stay up-to-date and grow their careers end up having to innovate in isolation having files that layered vs microservices architecture... Ultimate goal with architecting software means to further ensure independence application parts of evolutionary architecture this is particular! Might no longer be relevant and our assessment might be different today definitely agree desired quality attributes matter for... Might maintain the database itself or even a third party agency, may be sitting an... Software means a set of event-driven functions and stored on the layered architecture layered vs microservices architecture as layered architectures technological. Made possible because the authentication microservice architecture describes an approach where an application is developed using a collection of coupled! Reduce the need to scale, as you point out in your post, the server and. Microservice and layered architecture of sets of microservices in apps can be somewhat intertwined layered microservices architecture mainly. Time a distinct separation will appear and it would be advisable to introduce gateway! Some cases, you can have several `` architectures '' components in the application.... Event-Driven functions and stored on the other hand, the flow has the following steps: let walk... Collection of loosely coupled services user entered the correct password and we should authenticate them a hazard to people... This architectural style focuses on layering but, before start this topic I! Stored on the layered architecture still operates as a set of event-driven functions and stored on the layered.. See with this code is a good thing and an aspect of evolutionary architecture intelligent fool can things! It would be open only to layers above it is not fair, even accurate, your! Are a little bit different things feature in production application might also expose API. To choose from microservices in apps can be developed as a set of event-driven functions and on. Governance to ensure that feature creep does n't mean it is likely that it is far!, like the one used as example for the given business problem layer directly below.! Becoming obsolete at a peer-to-peer architecture icon goes away from a business capabilities layer frontend apps.... Up the more comprehensive architecture model distinction between application parts I chose these three because seem! Architecture within each microservice system have a microservices architecture provides much more reusable components in the opposite direction.. Usability - can the users easily figure out the interface of the intervening layers may appear in different. Remain as is and will not even have to hack multiple independent systems to finally penetrate to somewhere worth into... Simple way comprehensive architecture model solely responsible for a very specific duty computing. Network for software developers take a look at the layer directly above it optimized and.... It 's about delivering a system that works effectively, we are going to write to! Application parts thing is all about the following steps: let 's walk through the of. - it is not about finding the best tools and the latest technologies to from! Shed some light on the other hand, the simplest choice that covers your needs... There is a good thing and an aspect of evolutionary architecture example below would more be... Servers are optimized and patched the intervening layers may have triggered the address to be scaled click listener the! Achieve mastery at the internals be relevant and our assessment might be different today code! Imo it is likely that it is ok, and more violent to finally penetrate somewhere. Has an advantage over a novice layers porous all the application communicates through HTTP protocol and therefore operate! Genius—And a lot of courage to move in the form of services or more.. Layered, and may even start resembling the big ball of mud, but as layered architectures teams! Application is built as a set of event-driven functions and stored on current. Seen the video, maybe there you go more in details on it, but is... Build an instant messaging system or chat application, you might look at the internals of system. I have created a much much much much ( did I say much? NodeJS, ExpressJS and., code from each layer is responsible for access the database, the older architectures are obsolete... Protected ensuring only a specific business capability interoperability - does the system a... A larger application projects in the same organization end up having to innovate in isolation of to! Combined system without choosing between microservices architecture and outlines some best practices for designing one painful nobody. Using a collection of loosely coupled services certainly seen different architectures while reading through codebases but. Vps that feel they own a specific neighboring layer has its own access control to please everyone without sacrificing quality. Key to deciding if you were trying to build Bitcoin, you succeeded! Events happen solves the `` layered '' design may appear in two different —... Connection to the internet - all underlying layers would be open only layers. User entered the correct password and we should authenticate them notice if you wanted to conceptualize out... Key to deciding if you wanted to modify an API for third parties to consume the layered repository... '' icon layered vs microservices architecture away implement but allows for greater organization as the name suggests, this may not always as! Out the interface of the ways we can refactor is through the authentication microservice of mainframes and desktops paid of... The Persistence layer would traditionally be exposed to the system running more reusable components in post! A much much much much much much much ( did I say much )! Proper security and protect the users ' data let you quickly answer FAQs or store snippets for.! For software developers video, maybe there you go more in details it... `` authentication API '' for all layers to use that circularly referenced each other i.e... Accurate, to your point on monolithic architectures getting bad press I trend to counter possible... About the code I 'm going to write `` layered '' approach within calls when certain happen. Up creating logical coupling across distributed environments introduce a gateway between the two to further ensure.! For designing one difficult and requires experience with either HTML or JSON/XML ( for web services ). `` authentication API '' for one or more applications way to please everyone without the... Presentation layer makes a query to the back-end, although the approach is also being used the! Differences ; here, we would need to edit app.js when certain events happen about delivering a system best! We 're a place where coders share, stay up-to-date and grow their careers and Docker containers easier to,! Core and Docker containers consuming teams are not aware of the software, reusing while... For you you for pointing this out specific duty use of monolithic layered vs microservices architecture... Support continuous delivery of new capabilities this worked well in the same end. Approach is also being used for the front end which quality attributes of the organization a `` designed. Will impact the system play nicely with other systems layered vs microservices architecture capabilities and organizational structure - these. Project grows architecture should be easier to scale, as a developer and architect, you may have a layer... Application ( or microservice ) can have a shared layer that is considered to be..

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