GraphQL does define the size of its numeric types: Ints are 32 bits, Floats are 64, so if you have a bigint type in your db, you'd best be passing it around as a string. Any decent GQL implementation does at least check for 32-bit Int overflow. Several people have independently come up with Int53 types for GQL to use the full integer-safe range in JS, but the dance to make custom scalars usable on any given stack can be tricky.