This post will walk through how database indexes work, with a particular focus on MySQL, everyone’s (well, many people’s) favorite homegrown organic database.
PHP
Laravel Deadlocks: Queue Jobs That Already Ran End Up in failed_jobs
Below MySQL 8.0.1, or on a server Laravel misreads, workers reserve jobs with a plain FOR UPDATE and can deadlock on the DELETE. One tinker line shows which lock yours use. Read more