Once an application outgrows a single server, a reverse proxy sitting in front of multiple backend instances becomes necessary — routing traffic, handling SSL termination, and detecting unhealthy backends. Both Apache and Nginx can fill this role, and the right choice usually comes down to what's already running and what you need from it.
Nginx as a reverse proxy
Nginx's event-driven architecture handles a high volume of concurrent connections with a comparatively low memory footprint, which is part of why it's become the default choice for a lot of new infrastructure. Its configuration for reverse proxying, load balancing algorithms (round robin, least connections, IP hash for session affinity), and SSL termination is generally considered more straightforward to reason about.
Apache as a reverse proxy
Apache's mod_proxy and mod_proxy_balancer modules do the same job, and Apache remains a strong choice where you're already running Apache for other reasons (like .htaccess-dependent applications) and don't want to introduce a second web server into your stack purely for load balancing.
Health checks and failover
Whichever you choose, the load balancer needs to actually detect when a backend is unhealthy and stop routing traffic to it — a static list of backend servers with no health checking will happily send users to a server that's returning 500 errors. Configuring active health checks (not just relying on connection failures) is the difference between graceful failover and a partial outage that looks intermittent to users.
SSL termination
Terminating SSL at the load balancer, rather than on every backend server, centralizes certificate management and reduces CPU overhead on your application servers — but it also means the load balancer becomes a more critical single point that needs its own redundancy plan.
The practical answer
For most new setups without a strong existing reason to use Apache, Nginx tends to be the simpler starting point for reverse proxying and load balancing specifically. But "what are you already running, and does it do the job" is usually a better question than picking based on benchmarks alone.