@rimu if postgres ends up bogging down consider taking a look at https://github.com/valeriansaliou/sonic, it seems to be a nice compromise between the behemoths of elastic and meili and the simplicity of postgres fts.
(this instance i'm on is modified to use postgres fts and with almost 2 million posts in the database it's still quite fast, though search isn't as accurate as the 'simple' language in postgres fts not doing any language stuff and sharkey hasn't merged post language support just yet so i can't adjust it properly)