API Gateway vs Load Balancer vs Reverse Proxy vs Forward Proxy vs Service Mesh

These 5 components are one of the most confused concepts in system design.

They often appear in the same architecture diagrams.

But each solves a completely different problem.

Here's what each one actually does:

API Gateway

→ Single entry point for all API requests

→ Routes app and web clients to microservices and databases

→ Handles authentication, rate limiting, routing, API versions, and more.

Load Balancer

→ Distributes incoming traffic across multiple servers

→ App and web clients hit it through the internet

→ Optimizes resource usage and keeps things reliable

Reverse Proxy

→ Sits in front of your servers

→ Handles client requests on behalf of the backend

→ Helps improves security, SSL termination, caching, and performance.

Forward Proxy

→ Sits in front of your clients

→ Mediates outbound requests to the internet

→ Commonly used in enterprises for filtering, privacy, and access control.

Service Mesh

→ Control plane + data plane

→ Each service gets its own sidecar proxy

→ Handles retries, mTLS, traffic policies, observability, and service-to-service communication

The pattern once it clicks:

- Reverse proxy protects the server.

- Forward proxy protects the client.

- Load balancer spreads the load.

- API gateway manages the APIs.

- Service mesh manages everything between services.

Same building blocks.

Different problems they solve.

Which one trips people up the most in interviews? Curious what you think.