sliding-time.md

What is the best way to track frequency of events in the given period?

1. to find the number of events in in the last period T, find if the elapsed duration overlap
2. or check if the timestamp > current time - period
3. alternative is to round the time by the period, and increment the counter. The previous period can be cleared when a new one is created...

Implementation 1

if now - timestamp > period:
  increment counter

Implementation 2

Note that this is just a reverse of the formula above:

if now - period > timestamp:
  increment counter

Implementation 3

With this solution, the timestamp is recorded at every epoch (e.g. every 5 seconds, beginning with seconds 0, 5, 10...).

add event:
  counter[timestamp - timestamp % period]++
  
getting event:
  counter[now - now % period]