Technical Definition of API Monitoring
API monitoring refers to the practice of systematically executing automated requests to application programming interfaces (APIs) from synthetic testing nodes to verify availability, track response speeds, and validate the structural correctness of response payloads. Unlike basic website monitoring (which simply requests an HTML page and parses standard headers), API monitoring validates JSON or XML payloads to ensure that underlying database systems, auth policies, and microservice connections are functioning correctly.
In microservice architectures, pings are insufficient. A web application might load successfully and return an HTTP status code 200, but its checkout endpoint might return an empty JSON response or fail due to internal authorization issues. API monitoring uses assertions (such as JSONPath matches or regular expressions) to verify that specific data fields contain correct values.
Key Metrics Checked During API Audits
- HTTP Status Codes: Verifying that endpoints return the expected code (e.g. 200 OK for queries, 201 Created for checkouts).
- Response Latency: Tracking the time to first byte (TTFB) and transaction completion times to identify performance degradation.
- JSONPath Assertions: Matching specific JSON keys to check correctness (e.g., asserting that `$.success` evaluates to `true` or that `$.data.items.length` is greater than `0`).
- SSL Chain Integrity: Checking certificate validity and ensuring connections use TLS 1.3 encryption.
How It Works: Under the Hood of a Check Node
When an API monitor runs, our check nodes establish a TCP connection to the host, complete the TLS handshake, send the configured HTTP request (complete with headers, authentication keys, and query parameters), and parse the response. If the connection fails, or if a JSONPath assertion does not match the expected value, the check node routes alerts to your team.