A reverse proxy accepts client requests and forwards them to backend services.

It can terminate TLS, route traffic, compress responses, add security headers, perform access logging, enforce limits, and hide internal network topology.

Clients communicate with the public endpoint while the proxy communicates with internal application instances.

An API gateway is a specialized entry point that can provide routing, authentication integration, rate limiting, request transformation, observability, and aggregation across services.

In a microservice architecture, the gateway can present a unified external API while routing requests to multiple internal services.

However, putting too much business logic into the gateway creates a centralized bottleneck and makes the system harder to evolve.

Load balancers distribute requests across healthy instances.

Common strategies include round robin, weighted routing, least connections, and latency-aware routing.

Health checks can be shallow, such as checking whether a process responds, or deeper, such as checking critical dependencies. Deep health checks must be designed carefully because a dependency outage should not necessarily cause every instance to be removed from service.

Graceful shutdown is important: an instance should stop accepting new work while allowing active requests to finish.