B-Tree Indexes

B-Tree indexes are the default index. They are a B-Tree (a balanced tree with leaf nodes contained in arrays).

It can use the spaceship operator <=> (anything that fits comparisons)

As well, ranges, like GROUP BY and ORDER BY may use a B-Tree index.

B-Tree indexes can also be used on string matches, as long as you don't wildcard match on the beginning:

select * from users where name like '%name'; -- Will not use an index

select * from users where name like 'name%'; -- may use an index.