Wikipedia has a couple of non-timeseries examples[1].

I guess with timeseries you'd have something along the lines of:

   user |   time_range |  status 
  ======+==============+=========
      1 | [2018, 2021) | ACTIVE  
      2 | [2019, )     | ACTIVE  
      1 | [2021, )     | BLOCKED 

Where the PK is (user, time_range). (The time_range field being shortened to just year here for simplicity's sake.)

In PostgreSQL you can use the tstzrange[2] type. You could also only store one of the timestamps, but that would come at the cost of more complex queries.

[1]: https://en.wikipedia.org/wiki/Sixth_normal_form#Examples

[2]: https://www.postgresql.org/docs/current/rangetypes.html