APIs are the invisible conversations between services. When they fail, users don't see error messages—they see apps that mysteriously stop working. Here's how to watch what users can't see.
Database failures cascade—a connection timeout might hide replication lag, which hides disk exhaustion, which hides a backup that never completed. Each layer of checking reveals different truths.
DNS checks verify that your domain names resolve to the right IP addresses worldwide—because when DNS fails, nothing else matters.
HTTP checks pretend to be users visiting your site—verifying not just that servers respond, but that they respond correctly, quickly, and securely.
HTTP 200 OK means the server responded—not that it responded correctly. Content checks verify what users actually see.
Your site can show green across every health check while users can't complete a single purchase. Multi-step transaction monitoring catches what page-level checks miss.
Ping asks the network a simple question: are you there? Learning to interpret what the network says back—in latency, loss, and silence—is the real skill.
Your certificate answers one question for every visitor: 'Are you really who you claim to be?' SSL certificate monitoring ensures that answer stays 'yes'—catching expiration, broken trust chains, and revocation before browsers start warning users away.
A TCP port check asks the simplest question you can ask a service: are you there? Understanding what that answer means—and what it doesn't—is the foundation of network monitoring.
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