If you run a website, web application or API that‘s exposed to the public internet, using a reverse proxy server should be standard practice.
But what exactly is a reverse proxy, and why is it such an important technology?
In this comprehensive guide, I‘ll explain everything you need to know about reverse proxy servers as an experienced proxy expert and web developer. I‘ll cover:
- What is a Reverse Proxy and How Does it Work?
- Key Benefits of Using a Reverse Proxy
- Reverse Proxy vs Forward Proxy vs Load Balancer
- Common Use Cases and Examples
- Implementation Best Practices
- Disadvantages & Challenges to Consider
By the end, you‘ll understand what problem reverse proxies solve and whether implementing one could benefit your organization. Let‘s get started!
Contents
What is a Reverse Proxy Server?
A reverse proxy server sits in front of origin servers like backend application servers and databases, and receives requests from clients on behalf of those origin servers.
The reverse proxy forwards requests to the appropriate server and returns responses back to the client. From the client‘s perspective, it appears as though they‘re interacting directly with the reverse proxy server.
Some common examples of popular reverse proxy software include:
- NGINX
- HAProxy
- Apache Traffic Server
- Squid
- Varnish
- AWS Elastic Load Balancing
Unlike a forward proxy which sits in front of the client, a reverse proxy sits in front of the server. This provides additional security, performance, and flexibility to organize backend infrastructure.
Now let‘s go over why you‘d want to use a reverse proxy and the many benefits they provide.
Key Benefits of Using a Reverse Proxy
There are several reasons to use a reverse proxy server for websites, APIs, web applications, and microservices:
Security
One of the main benefits of a reverse proxy is security. The proxy hides backend web servers from external clients entirely. All inbound connections terminate at the proxy so attackers cannot directly interact with origin servers.
This provides protection against network-based attacks like DDoS, brute force login attempts, vulnerability scanning, etc. The proxy adds a layer of abstraction that makes discovering and targeting origin servers much more difficult.
According to Imperva, properly configured reverse proxies can mitigate over 60% of web application attacks.
Some other ways a reverse proxy improves security:
- Blocking unwanted traffic – IPs, countries, user agents, etc can be blacklisted
- Connection limiting – Prevents DDoS by limiting connections per client
- Web application firewall – Rules to filter malicious payloads in requests
- SSL/TLS termination – Decrypts traffic and sends internal requests over HTTP for performance
Load Balancing & High Availability
A reverse proxy can distribute requests across multiple backend origin servers to optimize performance and uptime. This acts as a "load balancer" to prevent any one server from becoming overloaded and failing.
If an origin server goes down, the proxy can automatically detect the outage and redirect traffic to other healthy servers. This provides high availability and resilience.
Load balancing improves resource utilization by spreading work evenly across available compute resources. Various load balancing algorithms and health checks are used under the hood to route each request intelligently.
Caching & Performance
Reverse proxies can greatly improve performance by caching static content closer to users. For example, a proxy server could cache static assets, HTML, API responses, database query results, and more. Serving cached content is much faster than having to compute every request on the backend.
Common caching methods include:
- Page caching – Entire pages are cached to avoid backend requests
- Fragment caching – Portions of pages can be cached for faster assembly
- HTTP caching – Caching objects based on response headers like Cache-Control
- Database query caching – Caching results of DB queries that rarely change
According to AWS, adding a caching layer with Amazon CloudFront led to a 68% improvement in latency for their customers.
Compression
Reverse proxies can compress backend responses using gzip or other algorithms before sending to clients. This saves bandwidth utilization and speeds up transmission across the internet.
Compression is useful for text-based content like JSON, XML, HTML, CSS, Javascript which compress very well. Image and video formats are already compressed so they typically don‘t benefit further from proxy compression.
Global Server Load Balancing
When running applications across multiple geographically distributed datacenters, a reverse proxy can route traffic based on the user‘s location. This is known as global server load balancing.
For example, a user in Europe could be routed to application servers in the nearest European datacenter to reduce latency. While US-based users would be routed to US-based servers.
This improves performance for globally distributed users and also keeps traffic within the region for any data sovereignty requirements.
Reverse Proxy vs Forward Proxy vs Load Balancer
To understand reverse proxies better, it helps to compare them against forward proxies and load balancers:
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Reverse Proxy – Sits in front of origin servers and forwards client requests to them.
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Forward Proxy – Sits in front of clients and forwards requests on their behalf.
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Load Balancer – Distributes requests across multiple backend servers. Reverse proxies can act as load balancers.
Load balancers focus purely on distributing requests for scalability and availability. Reverse proxies provide additional benefits like security, caching, compression, SSL offload, and more.
Many reverse proxy implementations like NGINX and HAProxy also include load balancing capabilities. But load balancers don‘t necessarily include reverse proxy features.
The table below summarizes some key differences:
| Reverse Proxy | Forward Proxy | Load Balancer | |
|---|---|---|---|
| Location | In front of origin servers | In front of clients | Between clients and servers |
| Primary Purpose | Security, caching, load balancing | Anonymity, circumvention | Load distribution |
| Caching | Yes | No | No |
| Security | Obscures servers, terminate attacks | Hides client IP | No |
| Compression | Yes | No | No |
So in summary, reverse proxies are very versatile and can provide security, performance and load balancing benefits.
Common Use Cases and Examples
Some common use cases where using a reverse proxy provides value:
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Application servers – Improve security, performance and availability for web apps and services.
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Microservices – Load balance across services and endpoints, handle SSL.
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APIs – Hide API servers, handle caching, rate limiting, security.
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Databases – Proxy queries for performance, availability and control.
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Internal services – Reverse proxy for inter-service communication, route to internal network.
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CDNs – Improve caching and performance by using a CDN as a globally distributed reverse proxy.
Popular examples of reverse proxy implementations:
- NGINX as a reverse proxy for web apps and APIs
- HAProxy for load balancing microservices
- Cloudflare CDN services in front of origin sites
- AWS ELB Application Load Balancer
Without a reverse proxy, clients would interact directly with application servers. Adding a proxy improves security, caching, reliability and load handling for these services.
Reverse Proxy Server Implementation Best Practices
If you decide to implement a reverse proxy, here are some best practices to follow:
Use TLS/SSL encryption
Encrypt connections between clients –> proxy and proxy –> backends with TLS/SSL to prevent eavesdropping on traffic.
Separate physical servers
Run the proxy on dedicated servers separate from your backend application servers for better security and availability.
Sticky sessions
Use sticky sessions to consistently route a client‘s requests to the same backend server. This preserves user session state.
Health checks
Configure health checks to automatically detect failed backends and stop sending traffic. Improves reliability.
Caching rules
Set optimal caching rules like Cache-Control headers to cache appropriate static assets and responses.
Fail open
If the proxy goes down, use fail open to route traffic directly to the backends. This reduces downtime.
Logging & analytics
Log traffic at the reverse proxy for analytics and visibility. Useful for security monitoring and performance.
Disadvantages & Challenges with Reverse Proxies
While reverse proxies provide significant benefits, there are also some downsides and challenges to consider:
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Increased complexity – More layers means more points of failure. Debugging and troubleshooting gets harder.
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Cost – Running robust reverse proxy servers incurs hosting and administration costs.
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Single point of failure – The proxy itself is a SPOF, so high availability configurations are needed.
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Performance overhead – Some proxy processing adds a bit of latency. This is usually negligible vs the caching benefits.
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Bandwidth costs – While caching reduces backend traffic, proxy egress bandwidth is increased.
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Security risks – Improper proxy configs can expose the backend servers if not careful.
These risks can be mitigated through good design practices. Overall, the benefits far outweigh the drawbacks for most externally-facing production workloads.
Conclusion
Adding a reverse proxy server can significantly improve the security, performance, reliability and capabilities of your websites, APIs and web applications.
Key benefits include obscuring backend servers, mitigating attacks, offloading TLS, load balancing across servers, caching static assets, compressing traffic and reducing latency for users.
Leading options like NGINX and HAProxy offer a robust feature set and are relatively easy to implement.
Just be sure to follow security best practices and the potential downsides can be minimized. For public-facing services on the internet, utilizing a well-configured reverse proxy is highly recommended.
So in summary:
- Reverse proxies sit in front of origin servers and forward client requests to them.
- Key benefits are security, load balancing, caching, compression and high availability.
- Common uses cases are protecting application servers, APIs, databases and internal services.
- Implementation best practices help maximize benefits and minimize risks.
I hope this guide has helped explain what problem reverse proxies solve and how they can benefit your organization! Let me know if you have any other questions.
