It’s a question I hear all the time: “What problem do microservices primarily fix?” Most people jump to answers like “performance” or “scalability.” While those are certainly benefits, they’re not the main event. The true, underlying problem that microservices were designed to solve is something far more fundamental to software development: cognitive load.
What is Cognitive Load?
Cognitive load refers to the total amount of mental effort that’s needed to perform a task. 🧠 It’s about how much a person’s working memory is being used. In software development, this translates to the amount of information a developer has to keep in their head to understand and work on a system. When the cognitive load is too high, it leads to mistakes, slower development, and burnout.
The Monolith’s Burden
For a long time, the dominant architectural pattern was the monolith. Think of it as one massive application that handles everything. This can be great for small projects, but as a system grows, it becomes a beast. A single change in one part of the code can have unforeseen consequences in another. Developers have to understand the entire application, or at least a huge chunk of it, just to make a small fix. This creates a massive cognitive burden. The sheer complexity of a large monolithic codebase is a primary source of high cognitive load.
Microservices: The Promise of Reduced Cognitive Load
Microservices were a response to this problem. They weren’t primarily about improving performance, though that’s a common misconception. The main goal was to reduce cognitive load and enable teams to develop faster. By breaking down a large application into smaller, independent services, each service becomes easier to understand and manage. A single team can be responsible for one or a few services, and they only need to understand the logic and dependencies of those specific services.
This shift allows teams to become experts in their domains. For instance, a team responsible for the “Order Processing” domain doesn’t need to know the intricate details of the “User Authentication” domain. This division drastically cuts down the amount of information each developer needs to hold in their head. The result? Faster development cycles, fewer bugs, and happier teams.
When Microservices Add to the Burden
Despite their promise, microservices can also increase cognitive load if not implemented correctly. Two main factors contribute to this:
- Technological Diversity: While using different technologies for different services can be powerful, an over-exaggeration of this can be problematic. If every microservice is built using a different framework (like Spring, Quarkus, or Micronaut), developers have to learn and maintain expertise in all of them. This creates a cognitive tax that can negate the benefits of the microservices approach. A more sensible approach is to standardize on a few technologies or use a polyglot approach judiciously.
- Poorly Defined Boundaries: If microservices are not properly separated by business domains, they can become just as complex as a monolith. If a single microservice handles too many processes or its responsibilities are not clearly defined, it can become a “mini-monolith.” This undermines the core principle of microservices and brings back the cognitive burden they were designed to solve.
The key to a successful microservices architecture is to ensure that services are genuinely small, single-purpose, and aligned with distinct business domains. This way, we can reap the benefits of reduced cognitive load and enable our teams to build amazing things faster.