[d503]

PostgresSQL's libpq supports nonblocking asynchronous operation, and node-postgres takes advantage of that.

http://www.postgresql.org/docs/9.1/static/libpq-async.html

https://github.com/brianc/node-postgres/blob/master/src/bind...

(notice the Connect method on line 325 of binding.cc)

At some level a client-server database driver isn't all that different from any other network client; you send a request over a socket and wait for a result. There's no reason you have to block while waiting.

Moreover some databases (like Postgres) let you receive asynchronous notifications signaled by transactions on other connections; that's how trigger-based replication systems like Bucardo do their thing.

http://www.postgresql.org/docs/9.1/static/sql-notify.html