"Apparently (after reading the documentation link provided by Tom) there can
be value to indexes when accessed with leading columns missing".
That is a new one on me too - interesting.
I suppose it comes down to testing at the end of the day - if you "set
enable_seqscan to false" and "EXPLAIN ANALYSE" your query then you will see
whether the indexes you create are used. Whether they are useful will
require you to set enable_seqscan back to true and see whether the optimizer
chooses to use them (but that will change as your data does).