From bulky apps to microservices: how app architecture evolved


For those who understand application development and architecture, the difference between modern practices and those used a decade or two ago is stark. Along with other IT changes, the evolution of app architecture has led to cost and time-savings for both companies and clients.

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Evolution of application architecture

Monolithic App Architecture

It's easy to understand how application architecture has improved by looking at how it once worked. Initially, large programs that required equally large programming teams ruled. This was known as monolithic architecture. A single app was responsible for every function. But while it may have been easy to create prototypes and only a single team was necessary for maintenance, app creation often lagged when using monolithic architecture, which relied upon different layers and sometimes became held up while waiting for data or user input. This increasingly became a problem as software might be outdated or no longer meet a company's needs by the time it was finished.

Furthermore, these apps were often difficult to scale as a company and its needs grew. These programs were large and often resource-intensive from the start. If they needed to scale, they might run up against server limitations. Upgrading, if possible, could be costly. To top it all off, a single bug in the code could break the entire program, further costing a company time and money while fixes were applied.

N-tier Architecture

To reduce some frustrations caused by monolithic architecture, we saw a move to n-tier architecture. In this model, apps consisted of multiple levels or tiers that allowed the development process to become more agile. Typically, three app tiers came together to form the overall project; however, there could be more tiers, and some people use "n-tier" when referring to just two app levels. The three basic tiers often consisted of the user-facing tier, the database that stored submitted data, and a middle tier that facilitated communication between the other tiers. These were sometimes called:

  • Presentation tier
  • Data tier
  • Logic tier

The benefits of n-tier architecture quickly became apparent. Different teams could work on each tier to produce results more quickly, maintain the software, or add new features. A problem with one tier didn't have to impact the rest of the software and was ultimately easier to pinpoint. N-tier also offered the benefit of hosting each tier on separate hardware if desirable, which decreased the likelihood of reaching a server's hardware limitations. It also became possible to scale up a single tier.

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This brings us to microservices, which quickly became an industry buzzword. In some ways, modern microservice methodology expands upon multiple-tier architecture and the service-oriented-architecture first introduced with Web 2.0. Each suite of software consists of many microservices, each of which focuses on its own task and can be quickly developed or fixed, even if there's only a single development team working on the app. For example, an online retailer's store, inventory, and account might be separate microservices. If a single microservice goes down, the rest of the app can remain functional. Because of their small size, microservices can be run from the cloud, and resource utilization concerns have been mitigated.

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Companies can also use microservices to more easily serve their clients. It's easy to add a new feature by incorporating a microservice or two. If customers respond well, great. If not, it's not a big deal to remove the microservice to return to the previous app setup or try something else. Customers can also provide targeted feedback about a single microservice.

The move to microservices also highlights a shift within some companies: developers, IT professionals, and operators often work much more closely than they once did. This isn't just a way to ensure that customers get the best experience; it may be necessary if different teams are responsible for the various microservices. This is one of the core principles of DevOps.


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