Quick lookup.
SITE DOWN ENTIRELY
Check from outside, then the provider's status, then your own logs.
WORKS FOR SOME PEOPLE ONLY
DNS caching, a partial deployment, or a caching layer.
SLOW AFTER A DEPLOYMENT
Caches not rebuilt, or a change introducing query multiplication.
INTERMITTENT FAILURES
Resource exhaustion, a failing dependency, or overlapping scheduled runs.
DISK FULL
Logs, backups held locally, or temporary files.
CERTIFICATE ERRORS
Expiry, a name not covered, or a clock wrong.
SCHEDULED TASKS NOT RUNNING
Wrong path, wrong runtime version, or the environment cron does not inherit.
DEPLOYMENT SUCCEEDED BUT NOTHING CHANGED
Caches, a worker holding old code, or deployment to the wrong location.
WORKS LOCALLY, FAILS IN PRODUCTION
Runtime version, dependency versions, environment values, permissions, filename case.
EVERYTHING SLOW, NO OBVIOUS CAUSE
Resource limits, a noisy neighbour, or something running on a schedule.
WHAT TO ESTABLISH FIRST, ALWAYS
What changed.
