Both cron and systemd timers can run a command at 2 a.m. The difference is what happens the night it doesn't run, and how long it takes anyone to notice. A comparison by failure family, with a decision rule, the same job written both ways, and how to debug each one when it goes quiet.
The rule went red at 02:04 and nobody found out until 09:15. Rule evaluation and notification delivery are two different systems, and only one of them is visible in the UI. A practical setup for Grafana alert notifications to email, Slack and Telegram, plus how to detect the day delivery quietly stops.
DirectAdmin gives each user one PHP-FPM pool, not each site. That single design fact explains most of the 502s on a busy shared box. Here is how to find the pool files, size pm.max_children from real memory numbers, set per-site limits that WordPress cannot override, and make the changes survive the next rewrite_confs.
High I/O wait is a symptom, not a diagnosis. It rises when nothing is wrong and stays flat when something is badly wrong, and it only sees one layer of the storage stack. This is how to read iowait and PSI correctly, then work through the five failure families that actually produce storage stalls: device saturation, memory pressure, synchronous writes, throttling, and latency that lives above the block layer entirely.
Migrations rarely fail loudly. The site stays up while mail, cron, certificate renewal and the write path break silently behind it. A post-migration checklist for the first 48 hours, ordered by how long each failure can hide rather than by subsystem.
The AWS Glue SAP OData connector demos beautifully and then drifts. A practical look at delta token invalidation, deletes that never delete, partitioning limits on ODP entities, and the licensing line between ODP-RFC and ODP-OData.
Readiness probes are necessary for Kubernetes zero-downtime rollouts, but they only close one of four gaps. Here is what actually drops requests during a deploy: the race between SIGTERM and endpoint propagation, probes that lie, surge settings that quietly delete capacity, and load balancers that never watched EndpointSlices in the first place.
WordPress tells you the mail was sent. The customer never got it. This is a working guide to the four places WordPress email deliverability actually breaks: PHP mail() transport, SPF lookup limits, DKIM alignment, and DMARC policy. Includes real diagnostic commands, a troubleshooting order, and what changed now that DMARC has moved onto the IETF standards track.
Docker's default logging driver writes container output to a JSON file with no size limit and no rotation. This is a practical guide to Docker log rotation: what the defaults actually do, why your daemon.json change did nothing, why deleting the log file did not free any disk, and how to choose between json-file, local, journald and shipping logs off the box.
The dashboard is fine for editing a post. It is a terrible tool for anything touching a thousand rows, twelve plugins or two servers. Here are the WP-CLI commands that save hours on migrations, plugin conflicts, stalled cron and integrity checks, grouped by the job that eats the time, with the failure modes each one hides.