Overview
A load balancer spreads incoming traffic across many identical backend servers so no single machine gets overwhelmed, while a reverse proxy sits in front of one or more servers to mediate, secure, and transform requests on their behalf. The two overlap heavily in practice — most modern reverse proxies (NGINX, Envoy, HAProxy) can also load balance — but the distinction matters when you’re deciding which capability you actually need to configure or scale for.
Comparison Diagram
Comparison Table
| Aspect | Load Balancer | Reverse Proxy |
|---|---|---|
| Primary goal | Distribute traffic across many backend instances to avoid overload | Mediate and forward requests to one or more origin servers on their behalf |
| OSI layer | Operates at L4 (TCP/UDP) or L7 (HTTP), often chosen for raw throughput | Almost always operates at L7, inspecting and rewriting HTTP requests |
| Routing decision | Algorithmic: round-robin, least-connections, weighted, or hashed | Rule-based: URL path, host header, headers, or cookies map to a backend |
| Backend topology | Assumes a pool of interchangeable, horizontally scaled servers | Commonly fronts a single origin, or routes distinct paths to different services |
| TLS termination | Supported, mainly to offload encryption before distributing load | Core use case, paired with header rewriting and request/response filtering |
| Caching & transformation | Not a typical feature; focus stays on connection distribution | Frequently caches responses, compresses, or rewrites headers/body |
| Failure handling | Health checks remove unresponsive nodes from the rotation automatically | Can retry or failover, but its main job is passing requests through correctly |
| Client-facing identity | May be invisible to clients, just an IP fronting the pool | Deliberately presents a single unified identity, hiding origin topology |
Key Differences
- A load balancer’s job is scaling out — spreading load across a pool; a reverse proxy’s job is mediating access to one or more origins.
- Load balancers lean on distribution algorithms, while reverse proxies lean on content-based routing rules.
- Reverse proxies commonly own TLS termination and response caching as first-class features, not just add-ons.
- Modern tools like NGINX or Envoy blur the line by implementing both roles in a single process.
- A reverse proxy can front a single server for security/caching alone, with no load distribution involved at all.
When to Use Each
Load Balancer
- Horizontal scaling: You have multiple identical app instances and need traffic spread evenly to keep latency and CPU load balanced.
- High-throughput L4 traffic: You need to distribute raw TCP/UDP connections with minimal overhead, without inspecting HTTP content.
- Zero-downtime deploys: Health checks let you pull unhealthy or draining instances out of rotation automatically during rollouts.
Reverse Proxy
- Centralizing TLS and auth: You want one place to terminate HTTPS, enforce headers, or add authentication in front of internal services.
- Hiding internal topology: Clients should see one hostname while requests are routed to different internal services by path or header.
- Response caching: You want to cache or compress responses close to the client without modifying the origin server itself.