Since operating DZLE lemmy instance for 18 days, almost 5 GB of the activity table has been accumulated, Had to go inside the postgres container to delete and vacuum those records before July 19. Now, the table size is about 1.8 GB.

Here is the current size of the tables as of this posting.

table size (MB)
activity 1834MB
comment_like 147MB
comment 107MB
post_like 80MB
person 67MB
comment_aggregates 26MB
post 13MB

It is still economical to run a small lemmy instance, but this will probably become problematic should the fediverse gets more active.