[Solved] Firebase matching substring

Firebase Database queries can only perform prefix matches, so strings starting with a specific string or starting with a range of string. It is not possible to query for strings ending with a specific value, nor those ending with a range of values.

If you really want to do this within Firebase, consider also storing the reversed strings in the database:

"321_1_0"
"321_3_0"
"654_52_0"

Then you can query for strings starting with 321 with

vehiclesQuery = db.getReference("vehicles").orderByKey().startAt("321").endAt("321\uf8ff");