If you know what causes downtime, you can catch it before it happens.
Server crashes, DNS failures, deploy errors, SSL expiry, traffic spikes, DDoS, database failures — the 10 most common causes of website downtime.
The most obvious cause: the server itself goes down. This can be a hardware failure on a VPS, a cloud provider outage (AWS, GCP, Azure all have regional outages), a container crash, or a Node.js process that OOM-kills. The fix is redundancy — multiple instances behind a load balancer — but for small sites, the practical fix is monitoring that tells you immediately so you can restart or switch providers.
Database failures are the second infrastructure cause. A database can run out of connections, hit a disk space limit, crash on a corrupt query, or lose replication sync. The application keeps running but every database-dependent page returns an error. Port monitoring on the database port (5432 for PostgreSQL, 3306 for MySQL) catches this — the port stops accepting connections before the app fully crashes.
DNS failures are insidious because everything looks fine from the server side. A DNS record expires, a nameserver changes, or a propagation issue leaves some users unable to resolve your domain. Your server is up, your logs are clean, but a percentage of users see "site not found." DNS monitoring (checking that your domain resolves to the expected IP) catches this — though SurePing doesn't currently offer DNS monitoring, so you'll need UptimeRobot or StatusCake for that specific check.
SSL certificate expiry is a common and embarrassing cause of downtime. Let's Encrypt certs expire every 90 days; if auto-renewal fails silently, the cert expires and every browser shows a security warning. SSL monitoring with a 14-day warning threshold prevents this entirely. Deploy errors — a bad code push, a missing environment variable, a failed migration — are the most preventable cause. A blue-green deploy or a canary release catches bad deploys before they affect all users, and monitoring confirms the new version is healthy before you cut over.
Traffic spikes (a viral post, a product launch, a Black Friday sale) can overwhelm a server that's sized for normal load. The server doesn't crash — it just gets slow enough that requests time out, which looks like downtime to users. Auto-scaling or a CDN with caching absorbs spikes, but if you're on a fixed-size server, monitoring tells you the moment response times degrade so you can scale up or enable a maintenance page.
DDoS attacks are a malicious version of a traffic spike — thousands of requests per second designed to exhaust your server's resources. A DDoS mitigation service (Cloudflare, AWS Shield) is the real fix, but monitoring tells you the attack is happening so you can enable mitigation. Finally, third-party failures: your payment gateway goes down, your auth provider has an outage, your CDN goes offline. You can't prevent these, but you can monitor the third-party endpoints you depend on and show a graceful error instead of a broken page.