When to use microservices (and when not to) - Deep Dive

Overview - When to use microservices (and when not to)

What is it?

Microservices is a way to build software by splitting a big application into many small, independent parts called services. Each service does one job and can work on its own. These services talk to each other over a network to make the whole system work. This approach helps teams build, update, and fix parts without affecting the entire application.

Why it matters

Without microservices, big applications become hard to change and slow to improve because everything is tightly connected. Microservices let teams work faster and handle more users by breaking the app into smaller pieces. This means better reliability, easier updates, and the ability to use different tools for different parts. Without this, companies struggle to grow and keep up with user needs.

Where it fits

Before learning microservices, you should understand basic software design and how monolithic applications work. After this, you can explore advanced topics like service orchestration, containerization, and cloud-native architectures.

Mental Model

Core Idea

Microservices break a big app into small, focused services that work independently but communicate to form a complete system.

Think of it like...

Imagine a restaurant kitchen where each chef specializes in one dish. Instead of one chef cooking everything, each chef focuses on their specialty, making the kitchen faster and easier to manage.

┌───────────────┐   ┌───────────────┐   ┌───────────────┐
│  Service A    │   │  Service B    │   │  Service C    │
│ (User Auth)   │   │ (Orders)      │   │ (Payments)    │
└──────┬────────┘   └──────┬────────┘   └──────┬────────┘
       │                   │                   │
       └───────┬───────────┴───────────┬───────┘
               │                       │
         ┌─────▼─────┐           ┌─────▼─────┐
         │  Database │           │  Message  │
         │           │           │  Queue    │
         └───────────┘           └───────────┘

Build-Up - 7 Steps

1

Foundation

Understanding Monolithic Applications

Concept: Learn what a monolithic app is and its limitations.

A monolithic application is built as one single unit where all parts are tightly connected. For example, the user login, product catalog, and payment system all live in one codebase and run together. This makes it simple to start but hard to change or scale because any change affects the whole app.

Result

You see why big apps become slow to update and hard to fix when everything is connected.

Understanding monoliths shows why breaking apps into smaller parts can solve growth and maintenance problems.

2

Foundation

What Are Microservices?

Concept: Introduce the idea of splitting apps into small, independent services.

Microservices divide an app into many small services, each doing one job well. For example, one service handles user login, another handles orders, and another handles payments. Each service can be built, deployed, and scaled separately.

Result

You grasp the basic idea of microservices as small, focused parts working together.

Knowing microservices helps you see how breaking complexity into pieces can improve flexibility and speed.

3

Intermediate

Benefits of Microservices Architecture

🤔Before reading on: do you think microservices always make apps faster and easier to build? Commit to your answer.

Concept: Explore the advantages microservices bring to software development.

Microservices allow teams to work independently on different parts, use different technologies for each service, and deploy updates without stopping the whole app. They also help scale parts that need more resources, like the payment service during sales.

Result

You understand why many companies choose microservices for large, complex apps.

Recognizing these benefits clarifies when microservices can improve development speed and system reliability.

4

Intermediate

Challenges and Costs of Microservices

🤔Before reading on: do you think microservices remove all complexity from software development? Commit to your answer.

Concept: Learn about the difficulties microservices introduce.

Microservices add complexity in communication between services, data consistency, and deployment. They require managing many services, handling failures gracefully, and monitoring performance. This overhead can slow teams if not managed well.

Result

You see that microservices are not a free lunch and need careful planning.

Understanding challenges prevents blindly choosing microservices and prepares you for their operational demands.

5

Intermediate

When to Choose Microservices

Concept: Identify scenarios where microservices are a good fit.

Microservices work well when apps are large, have many teams, need to scale parts independently, or require different technologies. For example, an e-commerce platform with separate teams for user accounts, product catalog, and payments benefits from microservices.

Result

You can spot real-world cases where microservices add value.

Knowing when microservices fit helps avoid unnecessary complexity in small or simple apps.

6

Advanced

When Not to Use Microservices

🤔Before reading on: do you think microservices are always better than monoliths? Commit to your answer.

Concept: Understand situations where microservices cause more harm than good.

Microservices are not ideal for small apps, startups, or teams without experience managing distributed systems. The overhead of running many services can slow development and increase bugs. Sometimes a well-structured monolith is simpler and faster.

Result

You learn to avoid microservices when they add unnecessary complexity.

Knowing when to avoid microservices saves time, money, and frustration in early or simple projects.

7

Expert

Balancing Microservices Trade-offs in Production

🤔Before reading on: do you think microservices always improve system reliability? Commit to your answer.

Concept: Explore how experts balance microservices benefits and costs in real systems.

In production, teams use techniques like service meshes, centralized logging, and automated testing to manage microservices complexity. They carefully decide service boundaries and use hybrid approaches, keeping some parts monolithic. They also monitor for cascading failures and design for graceful degradation.

Result

You understand the nuanced decisions behind successful microservices in real companies.

Seeing these trade-offs reveals that microservices require mature processes and tools to succeed.

Under the Hood

Microservices run as separate processes or containers, each with its own database or data store. They communicate over the network using APIs, often HTTP or messaging queues. Each service manages its own data and logic, which means data consistency across services requires special patterns like eventual consistency or distributed transactions. Deployment pipelines automate building and releasing each service independently.

Why designed this way?

Microservices were designed to solve the problems of large monolithic apps that were hard to scale and maintain. By splitting responsibilities, teams can work independently and scale only the parts that need it. Alternatives like modular monoliths or SOA existed but lacked the full independence and scalability microservices provide.

┌───────────────┐      ┌───────────────┐      ┌───────────────┐
│  Service A    │◄────►│  Service B    │◄────►│  Service C    │
│ (Own DB)     │      │ (Own DB)      │      │ (Own DB)      │
└──────┬────────┘      └──────┬────────┘      └──────┬────────┘
       │                      │                      │
       ▼                      ▼                      ▼
┌───────────────┐      ┌───────────────┐      ┌───────────────┐
│ API Gateway   │─────►│ Message Queue │─────►│ Monitoring    │
└───────────────┘      └───────────────┘      └───────────────┘

Myth Busters - 4 Common Misconceptions

Quick: Do microservices always make your app faster to develop? Commit yes or no.

Common Belief: Microservices always speed up development because teams work independently.

Reality: Microservices can slow development initially due to added complexity in communication, deployment, and testing.

Why it matters: Believing this can lead to adopting microservices too early, causing delays and frustration.

Quick: Do microservices guarantee better system reliability? Commit yes or no.

Common Belief: Microservices automatically make systems more reliable by isolating failures.

Reality: Microservices add network calls and dependencies that can cause new failure modes if not carefully managed.

Why it matters: Ignoring this can cause unexpected outages and harder debugging.

Quick: Is it true that microservices always require different programming languages per service? Commit yes or no.

Common Belief: Microservices mean using many different languages and technologies everywhere.

Reality: While possible, many teams use the same language across services to reduce complexity.

Why it matters: Misunderstanding this can lead to unnecessary complexity and harder maintenance.

Quick: Do you think microservices eliminate the need for good software design? Commit yes or no.

Common Belief: Microservices solve all design problems by splitting the app into parts.

Reality: Poor design still causes problems; microservices require careful service boundaries and data management.

Why it matters: Overreliance on microservices can hide design flaws and increase technical debt.

Expert Zone

1

Service boundaries are often the hardest part to get right and evolve over time with business needs.

2

Operational complexity grows with the number of services, requiring advanced tooling like service meshes and distributed tracing.

3

Hybrid architectures combining monolith and microservices can offer the best balance for many organizations.

When NOT to use

Avoid microservices for small teams, simple applications, or early-stage startups where speed and simplicity matter more. Instead, use a modular monolith or layered architecture until complexity justifies microservices.

Production Patterns

Real-world systems use API gateways for routing, circuit breakers for fault tolerance, and continuous integration pipelines for independent service deployment. Teams also adopt domain-driven design to define service boundaries aligned with business capabilities.

Connections

Domain-Driven Design

Builds-on

Understanding domain-driven design helps define clear service boundaries that match business functions, making microservices more effective.

DevOps and Continuous Delivery

Supports

Microservices rely heavily on automated deployment and monitoring, so knowing DevOps practices is essential to manage them successfully.

Human Organizational Structure

Analogous

Microservices mirror how teams are organized around business capabilities, showing how software design and company structure influence each other.

Common Pitfalls

#1 Starting microservices too early for a small app.

Wrong approach:

Splitting a simple app into many services before understanding the domain or scaling needs.

Correct approach:

Begin with a modular monolith and refactor to microservices only when complexity grows.

Root cause:

Misunderstanding microservices as a silver bullet rather than a solution for specific problems.

#2 Ignoring service communication failures.

Wrong approach:

Assuming network calls between services always succeed without retries or fallbacks.

Correct approach:

Implement circuit breakers, retries, and graceful degradation for inter-service calls.

Root cause:

Underestimating the complexity of distributed systems and network unreliability.

#3 Using different languages for every service without reason.

Wrong approach:

Choosing a new programming language for each microservice just because it's possible.

Correct approach:

Standardize on a few languages to reduce maintenance overhead unless a service has special needs.

Root cause:

Overvaluing technology diversity over operational simplicity.

Key Takeaways

Microservices split large applications into small, independent services that communicate over a network.

They help scale, update, and develop complex systems faster but add operational and design complexity.

Microservices are best for large, complex apps with multiple teams and scaling needs, not small or simple projects.

Successful microservices require careful service boundaries, strong DevOps practices, and monitoring.

Avoid common pitfalls like premature adoption, ignoring network failures, and unnecessary technology diversity.