APIs power virtually every digital interaction today, from loading your favourite social media feed to processing online payments. Yet many organisations treat API monitoring as an afterthought, only discovering issues when customers start complaining. API monitoring is the process of continuously observing and analyzing the performance, availability, and security of application programming interfaces to ensure they function correctly and efficiently.
The stakes couldn't be higher. UK businesses experienced 8.8 million internet outages in 2023, totalling 50 million hours of downtime and an estimated £3.7 billion in lost productivity. When your backend APIs fail, your entire digital presence fails with them.
Think of API monitoring as your system's health checks. Just as doctors monitor vital signs to catch health issues early, effective API monitoring tracks key metrics to identify problems before they cascade into system-wide failures.
API monitoring is the process of continuously checking for both the availability of your endpoints and the validity of their data exchanges. This extends beyond simple "ping tests" to encompass response times, error rates, and dependency health across your entire backend infrastructure.
The strategic approach involves three layers: availability monitoring (is it responding?), performance monitoring (how quickly is it responding?), and functional monitoring (is it responding correctly?). Each layer provides different insights essential for maintaining system health.
Health checks form the foundation of robust API monitoring. A service has an health check API endpoint (e.g. HTTP /health) that returns the health of the service, enabling automated systems to make intelligent routing decisions.
Liveness vs Readiness Checks
The liveness endpoint, often available via /health/live, returns the liveness of a microservice. If the check does not return the expected response, it means that the process is unhealthy or dead and should be replaced. Meanwhile, The readiness endpoint, often available via /health/ready, returns the readiness state to accept incoming requests from the gateway or the upstream proxy.
This distinction matters. A service might be alive but not ready to handle traffic due to dependency issues or startup procedures. Proper health check implementation prevents routing traffic to services that can't handle requests effectively.
Dependency Verification
Health checking microservices is simple. You just need a health check API endpoint for each service. You can then check whatever metrics are most relevant to that service – memory consumption, database connection, response time and so on.
Your health checks should verify critical dependencies: database connections, external API availability, and resource utilisation. If your API can't connect to its database, users shouldn't receive traffic until the connection is restored.
Modern applications often consist of dozens or hundreds of microservices, each requiring individual monitoring whilst maintaining visibility into the overall system health.
The shift towards microservice architectures in API design has also influenced health check strategies. An API might depend on numerous small, independently deployable services in a microservices setup. This complexity requires a coordinated monitoring approach.
Each microservice should expose standardised health endpoints, but the monitoring system must aggregate this information intelligently. A single slow database query in one service shouldn't immediately mark the entire system as unhealthy, but persistent issues should trigger escalation procedures.
Component-Level Monitoring
When you want to dive deep into the health of your API, a component-level status check is the way to do it. This comprehensive approach to monitoring looks at each individual component of an API system. Monitor databases, caches, message queues, and external integrations separately to pinpoint exactly where issues originate.
Status pages serve as your public face during incidents, providing transparency that builds customer trust even during outages. Downtime can be incredibly costly for any business - up to $5600 per minute. Downtime will happen but proper incident communication can save your business from poor reputation and impact customer trust.
Public vs Private Status Pages
The Private Status Page is vital for communicating audience-specific or sensitive updates to internal users. It integrates features like SSO, private logic, and Uptime user authentication, catering to various security requirements. Public status pages keep customers informed while private pages coordinate internal response efforts.
Effective status pages display real-time component statuses, historical uptime data, and clear incident communication. A status page API is a tool that allows you to manage and update a status page programmatically. This API is typically used by organizations to communicate service outages, maintenance windows, and performance metrics to users and stakeholders in real-time.
Response timing metrics: When monitoring an API's performance, it is crucial to dissect the overall response time into its constituent elements: DNS resolution, connection establishment, SSL/TLS negotiation, Time To First Byte (TTFB), and the data transfer phase.
Focus on these essential metrics:
Response Time: Track both average and percentile response times. A 500ms average might hide 5-second outliers affecting user experience.
Error Rates: Errors Per Minute (error rate) is the number of API calls with non-200 status codes per minute and is a critical metric for measuring how buggy and error-prone your APIs are.
Throughput: Monitor requests per second to understand traffic patterns and capacity requirements.
Dependency Health: Track the health of databases, external APIs, and other critical dependencies your services rely upon.
Manual monitoring doesn't scale. Monitoring of APIs should be done in real-time and 24 hours per day, seven days a week. Doing so ensures that any anomalies or errors that occur in a system are discovered and can be addressed swiftly.
CI/CD Integration
Another important practice in API monitoring is to shift the importance of monitoring and metrics left in the development and deployment process and integrate the monitoring with the CI/CD pipeline. This ensures monitoring coverage from the moment new code reaches production.
Alerting Strategy
Configure intelligent alerting that reduces noise whilst ensuring critical issues receive immediate attention. Use escalation procedures that automatically involve the right people based on incident severity and duration.
Health checks evaluate the current status of specific system components, while monitoring tracks performance metrics over time. Health checks provide immediate feedback on system health, whereas monitoring identifies trends and long-term issues.
Combine real-time health checks with historical trend analysis to build truly resilient systems. Look for patterns in your monitoring data: do certain APIs consistently slow down during peak hours? Are specific dependencies failing more frequently?
Proactive vs Reactive
The goal isn't just to detect failures quickly—it's to prevent them entirely. Use monitoring data to identify capacity constraints, performance degradation trends, and dependency issues before they impact users.
Strategic API monitoring requires the right tools and processes. Start with basic health checks for your most critical services, then expand to comprehensive monitoring as your system grows.
Remember: your customers don't care about your microservices architecture—they care about fast, reliable experiences. Effective API monitoring ensures your backend complexity never becomes their problem.
Ready to implement comprehensive API monitoring? Metrics+ offers robust uptime monitoring and status page capabilities to keep your backend systems healthy and your customers informed. Start monitoring your critical APIs today and ensure your digital infrastructure stays resilient.