Idea: Increase granularity of expiry timestamps from 1 second to milliseconds/nanoseconds?

[TysonAndre]

And separately from that, potentially allow floats for ttls in addition to integers.

Internally, APCu currently uses time_t. I believe this means that a key will expire at X seconds and .000000000 nanoseconds.

• i.e. currently, if I set a key with a TTL of 100 seconds at time X.123, then APCu stores it with an expiry of (X+100).000 with no fractional seconds, but I'd want it to expire closer to (X+100).123 instead

This would mean that for an application with a lot of frequently accessed, short lived keys backed by some (potentially slow) external service or db, there'd be a lot more requests to the external service at X.0 seconds than at X.5 seconds than at X.9 seconds , and if there's a bottleneck in the external service, requests at X.0 seconds would take longer to complete than requests at X.9 seconds.

• There's potentially workarounds such as storing the pair [$value, float $ttl] in apcu_store instead of just $value (or raising ttls) but that would not be as efficient as a native solution

Compared to when APCu was initially published in 2013, or APC in 2003

• PHP 7/8 is much faster than PHP 5 and has much lower memory usage per process
• Server CPUs can have many more cores
• CPUs have higher clock speeds and more ram

This can be done with gettimeofday and by changing times to be int64 and tp.tv_sec * 1000000 + tp.tv_usec