What are microservices?

Question

Accepted Answer

**Microservices** is an architectural style where an application is built as a set of **small, independently deployable services**, each owning one business capability and communicating over the network (HTTP, gRPC, or messaging).

## How it works

Each service runs in its own process, has its own data store, and can be developed, deployed, and scaled on its own. Teams own services end to end.

```text
          ┌──────────────┐
Client ─▶ │  API Gateway │
          └──────┬───────┘
     ┌───────────┼───────────┐
     ▼           ▼           ▼
 ┌────────┐ ┌─────────┐ ┌──────────┐
 │ Orders │ │ Payments│ │ Shipping │   ← each: own code + DB
 └───┬────┘ └────┬────┘ └────┬─────┘
     ▼           ▼           ▼
  ordersDB   paymentsDB   shippingDB
```

## Key traits

- **Single responsibility** — one service per business capability.
- **Independent deployment** — ship one service without redeploying the whole app.
- **Decentralized data** — each service owns its database.
- **Network communication** — services talk via APIs or events, not in-process calls.

## Trade-offs

You gain independent scaling and team autonomy, but pay with distributed-systems complexity: network failures, eventual consistency, and harder debugging.

## Why it matters

Microservices let large teams move fast in parallel because each squad can deploy its own service without coordinating a giant release.

They also let you scale and harden the parts that need it, instead of scaling one monolithic block.

But the complexity is real, so the style only pays off when the organization and problem are large enough to need it.