A long time ago, in a galaxy far, far away, ‘threads’ were a programming novelty rarely used and seldom trusted. In that environment, the first PostgreSQL developers decided forking a process for each connection to the database is the safest choice. It would be a shame if your database crashed, after all.
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Since then, a lot of water has flown under that bridge, but the PostgreSQL community has stuck by their original decision. It is difficult to fault their argument, as it’s absolutely true that: