Practical notes and questions about building websites, applications, APIs, databases, and CMS platforms.
Two database transactions can each be valid on their own and still become unable to continue when they run together. One holds a lock the other needs; the second holds a lock the first needs. MariaDB then returns a message that sounds alarming: Deadlock found…
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A post row says its author is user 42, but user 42 does not exist. The application can hide the missing name, return an error, or quietly s…
One article can quietly acquire several addresses. A tracking parameter creates one URL, a print view creates another, and an old route may…
A form saves a new record, the browser shows a success page, and then someone presses refresh. Should that refresh display the result again…
A large download stops halfway. The local file is still there, so asking for only the missing bytes sounds obvious. But what if the file be…
A deployment replaces PHP files on disk, but that does not by itself answer which compiled instructions a long-running PHP process will exe…
An application can finish generating a response quickly while the person downloading it is on a slow connection. Who should wait in that si…
Two people open the same article in an editor. Both see revision 17. One fixes the introduction and saves revision 18. The other, still loo…
An Nginx configuration can be valid and still be wrong. A proxy rule may point to the wrong upstream, a hostname may fall into the default …
Nginx returns a 502 response, and the error log mentions a Unix socket used by PHP-FPM. It is tempting to make that socket writable by ever…
