[qopp]

Just to keep it in memory? Postgres does this already-- it will put tables or parts of tables in memory to speed up reads [1].

[1] Source: https://momjian.us/main/writings/pgsql/hw_performance/

[cobbzilla]

It's not about "just" keeping it in memory, it's about handling hundreds of updates per second without creating un-vacuumable bloat (per description in OP's link).