what a reverse proxy is (educational)

what a reverse proxy is (educational)

A reverse proxy is a server that sits between clients and one or more backend servers, accepting requests from clients and forwarding them to the appropriate internal service on their behalf. For a beginner, it helps to think of the reverse proxy as a receptionist for a building: it receives visitors, decides which room to send them to, and may also check their credentials and provide directions. Unlike a forward proxy, which represents clients to the outside world, a reverse proxy represents servers to clients, making the internal topology of a service invisible to the public internet. Understanding this basic role is the first step to appreciating the different features and use cases a reverse proxy can provide.

The way a reverse proxy works in practice is straightforward and can be described as a simple flow. A client, such as a web browser, sends a request to a public IP address or domain name that resolves to the reverse proxy. The reverse proxy examines the request and uses configured rules to select which internal server should handle the work. The chosen backend server sends its response back to the reverse proxy, which in turn forwards that response to the client. From the client's viewpoint the proxy is the server, and the backend servers are hidden. This arrangement allows you to present a single front door to many services and to control traffic centrally.

Common uses and capabilities of a reverse proxy include several practical functions that are useful in modern infrastructure. A reverse proxy can balance load across multiple application instances to improve capacity and resilience, terminate TLS so that internal servers need not manage certificates, cache responses to reduce load and improve latency, compress or optimise responses for delivery, and enforce routing rules such as virtual hosting or path-based forwarding. It is also commonly used to enforce simple security policies like blocking malicious requests, applying rate limits, or centralising authentication before traffic reaches sensitive systems.

• Load balancing to distribute requests across servers.
• TLS termination so certificates are managed at the edge.
• Caching and compression to speed up responses.
• Routing and virtual hosting for multiple domains or paths.
• Security controls such as IP allow/deny and rate limiting.

When deploying a reverse proxy there are a few practical considerations to bear in mind so you avoid common pitfalls. You will typically need to configure how client IP addresses are preserved, commonly through headers such as X-Forwarded-For, because logging and access control often depend on the original address. Session stickiness or affinity may be necessary for some applications that rely on in-memory session state, so plan for either sticky sessions or a shared session store. Health checks and graceful draining ensure that backends are removed from rotation cleanly during maintenance. Monitoring, logging and centralised metrics for the proxy itself are important because it becomes part of the critical path for user requests.

There are clear benefits to using a reverse proxy, but there are also trade-offs to consider. On the positive side, a reverse proxy can improve performance through caching and compression, make certificate management simpler by centralising TLS, and provide a single point to apply security and routing rules which reduces configuration duplication. On the downside, it introduces an additional hop in the request path and can become a single point of failure if not deployed with redundancy, so it is normal to run multiple proxy instances behind a load balancer or in an active-active configuration. Complexity increases when you add features such as dynamic service discovery, advanced routing or API gateway capabilities, so start small and add features as needs evolve.

For beginners who want to experiment, a practical first step is to run a single reverse proxy in front of a couple of simple backend services in a development environment to get comfortable with routing rules and TLS termination. Common open-source options that many people start with include Nginx and HAProxy because they are widely used and well documented, and there are simpler managed solutions if you prefer less operational overhead. If you want to read more about infrastructure topics and examples of common reverse proxy patterns, visit the Infrastructure label on this site for related posts and guides at other Infrastructure articles. This beginner's overview should give you a foundation to make informed choices when you next need to route, secure or optimise traffic for a service. For more builds and experiments, visit my main RC projects page.