Practical notes and questions about building websites, applications, APIs, databases, and CMS platforms.
A visitor requests a URL that has never existed. The page clearly says “not found,” offers a search box, and links back to useful sections. Yet the response line says 200 OK. To a person, the page looks like an error. To an HTTP client, the request succeeded.…
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A client sends POST /orders. The server may have committed the order, but the response disappears during a timeout. Should the client retry…
Two registration requests ask for the same username at nearly the same time. Each request checks the database, and each sees that the name …
A PHP endpoint receives bytes, not trustworthy application data. Calling json_decode() is necessary when those bytes contain JSON, but a su…
An API can return 422, but a client may still need to know whether a title is missing, a date is invalid, or a state transition is no longe…
A PHP endpoint has selected the correct PDF, checked that the current user may download it, and is ready to send the response. One small qu…
A list can look stable while someone reads it and still move underneath the pagination controls. Suppose page one shows the newest 20 artic…
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 o…
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…
