this sounds like the best plan - to allow GIS querying/filtering at the earliest possible..
what I don’t understand is how it can be slow currently, what is the current code/flow?
this I don’t quite understand do you have multiple listeners to the NOTIFY? - I would have one listener that gets the post INSERT and then queries/filters the user lat/lng data against the post lat/lng and does the appropriate channel broadcast(s) - also do you have one channel that all users share or do you have per user channels?
