From Monoliths to Microservices: An Introduction to Serving Patterns

Big Picture Shift

• Moving from single-node patterns → multi-node distributed systems
• Systems are now:
  • Loosely coupled
  • Communicating over network APIs
  • Coordinated with parallel + asynchronous calls

Monolith vs Microservices

Monolith

• Everything in one application/container
• Tightly coupled
• Hard to scale selectively

Microservices

• App split into many small services
• Each service:
  • Runs independently
  • Communicates via APIs

Why Microservices Are Useful

1. Better team ownership

• Small services → owned by small teams (“two-pizza teams”)
• Less coordination overhead

2. Decoupling via APIs

• Services interact through stable contracts
• Teams can:
  • Develop independently
  • Deploy independently

3. Abstraction + Encapsulation

• Abstraction
  • Use a service without knowing how it works
• Encapsulation
  • Hide implementation details

Together:

• Reduce complexity
• Improve developer productivity

4. Independent scaling

• Each service scales differently:
  • Stateless → horizontal scaling
  • Stateful → sharding, etc.

Much more efficient than scaling a full monolith

Downsides of Microservices

1. Debugging is harder

• Failures span multiple services & machines
• No single place to inspect

2. Higher system complexity

• Many:
  • Communication patterns (sync, async, messaging)
  • Coordination mechanisms

3. Risk of over-fragmentation

• Too many small services = bad

• Rule of thumb:

  If services > engineers → probably overdoing it

4. Performance & cost overhead

• Network calls instead of in-process calls
• Each service has CPU/memory overhead

Why Patterns Matter

• Distributed systems are complex → patterns help:
  • Standardize design
  • Improve debuggability
  • Reuse proven solutions

Patterns = shortcuts to good architecture

Mental Model

Monolith:
[ All features in one app ]

Microservices:
[ Service A ] ↔ [ Service B ] ↔ [ Service C ]
        (API communication over network)

One-line Summary

Microservices break applications into independently deployable services that communicate over APIs, improving scalability and team autonomy—but at the cost of higher system complexity and debugging difficulty.