[justsomehnguy]

  cat /api/version.txt
  2023.01.01

  ls /api
  version.txt data.zip

[accrual]

Or maybe encode the version into the filename? It would overwrite if nothing changed, and the previous versions would remain available.

    2023.01.01-data.zip

[justsomehnguy]

That requires preprocessing on the client and there are some ppl who has.. weird assumptions about how the dates should be written.

The version file can be quired at least the two ways:

the ETag/If-Modified-Since way (metadata only)

content itself

The best part with the last one - you don't need semver shenanigans. Just compare it with the latest dloaded copy, if version != dloaded => do_the_thing