Choose CDN when...

• •Your application serves static assets (images, CSS, JavaScript, videos) to users across multiple geographies and you need to minimize latency.
• •You want to reduce origin server load by caching responses at the edge, especially for read-heavy workloads with high cache hit ratios.
• •DDoS protection is a concern and you want a globally distributed network to absorb volumetric attacks before they reach your infrastructure.
• •You need to minimize TLS handshake latency for global users by terminating SSL at edge locations near the user.
• •You want edge compute capabilities (Cloudflare Workers, CloudFront Functions) to run lightweight logic at the edge without round-tripping to the origin.

Choose Load Balancer when...

• •You need to distribute traffic across multiple backend servers for horizontal scaling within a data center or region.
• •Sophisticated health checking and automatic failover are required to route traffic away from unhealthy servers within milliseconds.
• •You need advanced routing capabilities: path-based routing to different service clusters, weighted routing for canary deployments, or sticky sessions for stateful applications.
• •Your architecture requires connection pooling and keep-alive management between the load balancer and backend servers to reduce connection overhead.
• •You are implementing blue-green or rolling deployments that require precise traffic shifting between application versions.

Do I need both a CDN and a load balancer?

For most production web applications, yes. The CDN handles global content distribution, caching, and DDoS protection, while the load balancer distributes dynamic requests across your backend servers. They solve different problems and complement each other. Small applications with a single server and local user base may not need a CDN, and purely static sites may not need a load balancer.

Can a CDN replace a load balancer?

Not fully. While modern CDNs offer basic load balancing features (routing to multiple origins), they lack the sophisticated health checking, connection pooling, session affinity, and deployment routing that a dedicated load balancer provides. CDNs are optimized for caching and edge delivery, not for distributing dynamic traffic across backend servers.

How does a CDN reduce latency?

A CDN reduces latency in three ways: (1) by serving cached content from edge PoPs physically close to the user, reducing network round-trip time; (2) by terminating SSL at the edge, eliminating the need for the TLS handshake to travel to a distant origin server; and (3) by optimizing network paths between edge and origin using private backbone networks that are faster than the public internet.

What is the difference between Layer 4 and Layer 7 load balancing?

Layer 4 (transport layer) load balancers route traffic based on IP address and TCP/UDP port without inspecting packet contents. They are fast and protocol-agnostic. Layer 7 (application layer) load balancers inspect HTTP headers, URLs, and cookies to make routing decisions. They enable path-based routing, header-based routing, and SSL termination but add processing overhead.

How do CDNs handle cache invalidation?

CDNs offer several cache invalidation strategies: TTL-based expiration (content expires after a configured time), purge APIs (immediately remove specific URLs or patterns from all edge caches), stale-while-revalidate (serve stale content while fetching fresh content in the background), and cache tags or surrogate keys (purge groups of related content atomically). The right strategy depends on how frequently your content changes and how tolerant users are of stale data.