Custom Software & API Integrations

A proxy, gateway, or application layer can transform an upstream response, so the client’s status and message may differ from the server’s underlying error. What to check Trace a request ID across client, gateway, application, and provider logs. Compare status codes, response bodies, timeout settings, and any sanitization or retry behavior....

Large API responses can exceed payload limits, memory, timeout, or pagination assumptions. Small test requests may pass while real data fails. What to check Compare response size, pagination, compression, timeout, client memory, gateway limits, and error stage. Use a sanitized sample and identify whether partial data was stored. Recommended next step...

An integration can fail after token rotation if one service still uses a cached credential or the new token has different permissions or audience. What to check Check token expiry, issuer and audience, scopes, secret deployment, cache behavior, clock skew, and which integration instances have reloaded credentials. Never place token values in logs....

If two connected systems can edit the same record, later updates may overwrite newer information or create conflicting values. What to check Identify field ownership, update timestamps, version numbers, conflict behavior, retry logic, and audit history. Test concurrent edits with non-production records. Recommended next step Define a source of truth...

Some APIs accept a request and return success while processing continues asynchronously. A caller may assume completion and read results too early. What to check Check response semantics, task or operation IDs, status polling, callbacks, and eventual consistency expectations. Confirm how failures are reported after acceptance. Recommended next step...

An API client may resend a request after a timeout even when the server completed the notification. Without deduplication, the recipient can receive repeated messages. What to check Compare request IDs, provider status, retry timing, idempotency support, and delivery events. Distinguish duplicate API calls from separate business events. Recommended...

Asynchronous systems can deliver updates out of order, causing an older event to overwrite newer state. Arrival time alone may not reflect the source event sequence. What to check Compare event timestamps, sequence numbers, version fields, retries, and consumer concurrency. Identify whether the receiving system has a monotonic update rule. Recommended...

A provider may change rate limits or apply limits differently by endpoint. An integration that sends bursts can begin failing even when average volume appears unchanged. What to check Review response codes and headers, request concurrency, retry behavior, quota scope, and recent provider notices. Identify whether failed requests are safe to replay....