Guides
A useful place to start, with a route to the related result.
Guides 241–264 of 348
Troubleshooting guide
Verifying SendGrid's signed event webhook: why the raw body matters
How SendGrid signs its event feed, why re-serialised JSON breaks verification, and how to test that a forged event flags nobody.
Troubleshooting guide
Twilio says sent, then delivered, then sent again: store a final state, not the latest arrival
Rank Twilio message statuses so an out-of-order callback never overwrites a final result, and keep error codes as information rather than rules.
Troubleshooting guide
Twilio callback checks fail or never fire: the exact URL and what test credentials cannot do
Why Twilio's request signature depends on the exact URL it called, and why test credentials cannot show delivery callbacks at all.
Troubleshooting guide
Alerting Slack from your app: webhook or bot token, and how to avoid slowing or flooding it
Choose between an incoming webhook and a bot token, keep alerts outside the customer's request, and respect Slack's per-channel rate limit and Retry-After.
Troubleshooting guide
Slack events hit your endpoint twice, or not at all: signature, timestamp and the three-second rule
How Slack signs events, why the raw body and a five-minute window matter, and how to reply in time without running the work twice.
Troubleshooting guide
Direct uploads with signed storage links: what the link allows, how long it lasts and what it does not check
A signed upload link is a bearer token tied to the credentials that made it; design the key, lifetime, after-upload checks and the cleanup of uploads nobody confirms around that, and note where S3-compatible stores differ.
Troubleshooting guide
Rate limited or timing out: wait as the provider asks, then back off with spread
Read Retry-After in both of its forms, add capped exponential backoff with randomness, bound the attempts and total time, and test the policy with a scripted fake provider.
Troubleshooting guide
A timed-out create may have worked: making retried writes safe
Three ways to avoid duplicate records when retrying a create, from provider idempotency keys to lookup and an attempt ledger, and what to do when none is possible.
Troubleshooting guide
Website form to Pipedrive: store first, match by email, create a linked lead, respect the limits
The order of calls, the API versions, the matching rule, the rate limits and the outage design for pushing a form enquiry into Pipedrive without losing it, and the lookup that keeps a lost reply from creating a second lead.
Troubleshooting guide
Keep a register of your integrations: what expires, what limits you and what gets retired
A one-page register of each outside service's credentials, owners, dates and limits, with documented examples of what ends and where to watch for notices.
Troubleshooting guide
Certbot renewal on your own server: dry run, schedule, reload hook and the old 30-day rule
How to check that Let's Encrypt renewal will work before the certificate expires, what actually schedules it, why the web server must reload, and why the renewal threshold changed.
Troubleshooting guide
Certificate validation fails: port 80, redirects, DNS challenges and rate limits
What the HTTP-01 challenge needs from your server, when the DNS-01 challenge is the right choice, and how failed attempts can lock you out for an hour or a week.
Troubleshooting guide
Terraform: read the plan like a diff, keep secrets out of state, and protect what holds data
How to read a plan before applying, what a saved plan file and state can expose, when a module is worth writing, and the limits of prevent_destroy and import.
Troubleshooting guide
Kubernetes pod will not start: CrashLoopBackOff and ImagePullBackOff are different problems
How to read container state, previous logs and events to tell a crashing container from an image that cannot be pulled, and which manifest or values change fits each.
Troubleshooting guide
Pods Running but not Ready, and rollouts that never finish: probes and the progress deadline
What liveness, readiness and startup probes each do, why a liveness probe can cause an outage, how a Deployment reports a stalled rollout, and how to roll back safely.
Troubleshooting guide
Moving a PostgreSQL database to a new server: dump, roles, restore and the cutover freeze
What pg_dump does and does not include, how to rehearse a restore, how roles and ownership affect it, and why writes must stop before the final dump.
Troubleshooting guide
Reading a cloud bill: where the money usually hides and what to check before deleting
A first pass through a cloud bill: group by service and usage type, compare months, look for idle volumes and addresses, and check use and back up before any removal.
Troubleshooting guide
Compose starts your app before the database is ready: health checks and startup order
Why depends_on alone does not wait for a database, how a health check that tests the real connection path and the service_healthy condition prevent the start-up failure, and the restart and redeploy habits a single-VPS Compose stack needs.
Troubleshooting guide
Your container port is open to the internet even though ufw says it is closed
How Docker-published ports sit outside the rules ufw manages, how to bind a port to the loopback address, and how to prove from outside which ports a server really exposes.
Troubleshooting guide
A disk filling with logs: three sources, three different limits
Why container logs, the systemd journal and application files each need their own size limit, what the defaults are, which changes apply only to new containers, and how to test a rotation rule safely.
Troubleshooting guide
Turn off SSH passwords without locking yourself out: order, files and checks
The safe order for key-only SSH and a deny-by-default firewall, why the first value wins in sshd_config, how to read the effective settings, and what to keep open while you test.
Troubleshooting guide
Automatic security updates on Ubuntu: what is enabled, what is not, and the reboot question
How unattended-upgrades decides what to install, how to run a dry run, where it logs, why a package can install and still need a restart, and what an honest monthly review adds.
Troubleshooting guide
systemd service that will not stay up: restart rules, start limits and start types
Why a unit does not restart by default, how Restart, RestartSec and the start limits interact, what Type changes, and how to test a service by killing it.
Troubleshooting guide
Secrets in an env file? Protected alternatives on Compose, systemd and Kubernetes, and the rotation order
Why environment variables are a weak place for secrets, how Compose secrets, systemd credentials and Kubernetes Secrets differ, and a rotation order that does not take the app offline.
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