Keyv isn't fast enough for concurrent requests

[AlmostEfficient]

Area
Making concurrent requests with /faucet and setting 'lastTx' in Keyv (index.js)

Expected behaviour
Every request after the first is told to wait for 15s to make a new request.

Actual behaviour
A few requests right after the first aren't stopped by the lastTx time check. This is because Keyv hasn't set lastTx yet.

Need to either use Redis or just do this in memory. Will explore options.