functional requirements:

1.2k to 3k WPS

155k to 350k RPS

3k * 365

solution:

at 3k (worst case) it's only 1.5 million tiny urls a year, which is not that bad. a single RDMS instnace can handle that many.

at 350k RPS though RDMS can't, so we can setup a radis cache.

we can only have these radis caches in servers near different user zones.

## what the server does:

cache is updated on write. cache has a ttl for each item. when it's time to die, the cache saves on call.

there's a caching service that removes that cache when it's time to die