Anyevent::dbi is an anyevent extension, you need to make sure that you use and run a supported event loop. this module implements asynchronous dbi access by forking or executing separate "dbi-server" processes and sending them requests. it means that you can run dbi requests in parallel to other tasks. the overhead for very simple statements ("select 0") is somewhere around 100% to 120% (dual/single core cpu) compared to an explicit prepare_cached/execute/fetchrow_arrayref/finish combination.