Real issues encountered during TicketMe's development, their root causes, and how they were resolved. Documented here both as a reference and as evidence of the debugging process behind this project.
Symptom: Tests for register_handler were silently executing list_events_handler's code instead (visible via log output showing the wrong handler's log messages).
Cause: Both handlers' files are named app.py. Python caches imported modules by name in sys.modules, so a plain import app in a second test file returned the already-cached first module.
Fix: Load each handler explicitly by file path using importlib.util.spec_from_file_location() with a unique module name per handler, bypassing sys.modules name collisions entirely.
Symptom: ValidationException: Attribute name is a reserved keyword; reserved keyword: capacity
Cause: DynamoDB reserves several hundred words (including common field names like capacity, status, name, count) for its own query syntax. Using them directly in expressions fails.
Fix: Use ExpressionAttributeNames placeholders (e.g., #cap mapped to capacity) in any UpdateExpression or ConditionExpression.
Symptom: Browser console showed CORS errors; the underlying OPTIONS request returned a 500 from API Gateway.
Cause: The MOCK integration's request template only matched application/json, but browsers often send preflight requests without a matching Content-Type, and API Gateway had no fallback behavior defined.
Fix: Added passthrough_behavior = "WHEN_NO_MATCH" to the MOCK integration, allowing it to proceed even when the Content-Type doesn't match a defined template.
Symptom: Looking up registrations by email always returned zero results, despite matching data existing in DynamoDB.
Cause: CloudWatch logs revealed the Lambda received the email as jane%40example.com instead of jane@example.com — API Gateway was not decoding the path parameter before invoking Lambda.
Fix: Explicitly decode path parameters in the handler using Python's urllib.parse.unquote(), rather than relying on implicit upstream decoding behavior.
Symptom: New feature branches were repeatedly missing files that had, in theory, already been merged — VS Code showed tracked files as deleted/red.
Cause: Several Pull Requests were accidentally merged into main instead of develop (an easy mistake via GitHub's web UI dropdown), leaving develop stale relative to main and causing new branches created from develop to miss recent work.
Fix: Adopted git status as a mandatory first check before every commit, and switched to opening PRs via the GitHub CLI (gh pr create --base develop --head <branch>), making the base branch an explicit, visible part of the command rather than a UI element that's easy to overlook.
Symptom: Validate Terraform configuration failed in GitHub Actions with Error: Terraform exited with code 3.
Cause: Hand-edited .tf files had inconsistent whitespace/alignment, which terraform fmt -check -recursive (run in CI in check-only, non-mutating mode) correctly flagged as non-canonical formatting.
Fix: Run terraform fmt -recursive locally before every commit touching .tf files — now a standard habit alongside terraform validate.