What are health checks and why are they important?

Health checks verify service/component status for load balancing and alerting. Types: liveness (is process running), readiness (can handle traffic), deep health (dependencies working). Implementation: HTTP endpoint (/health, /ready), return status code 200 or 503. Used by: load balancers (route traffic away from unhealthy), container orchestrators (restart unhealthy containers), monitoring (alert on failures). Design: fast execution, check critical dependencies, don't cache. Essential for self-healing systems.