Weak example to ask precisely when the plane is at X feet, not an inch higher/lower - this is more typically a range query, and the Postgres range datatype is quite good at this, notably GiST indexes for overlap queries: https://www.postgresql.org/docs/9.3/functions-range.html#RAN... https://www.postgresql.org/docs/current/rangetypes.html#RANG...

PostgreSQL allows for all of that: User-defined types with user-defined index structures and whatnot. PostgreSQL is great and flexible, yet transaction safe and fast. You should really try it. It is one of the highest-quality FLOSS projects I have ever seen, not just in term of code quality, but also in terms of project and community management.