&gt;  I think Datomic which has been doing time series data for years now answers the &quot;what’s the big deal&quot; question for me:<p>This is known as &quot;time travel queries&quot;. Postgres supported this back in the original version from the 1980s but then they took it out in 1997 because it takes up too much disk space.<p>It&#x27;s trivial to do in an MVCC system. You just turn off garbage collection (vacuuming in PSQL parlance).