idea
- hash url's by sha512-256
- digest that sha512-256 hash into base62 (a-zA-Z0-9)
- truncate the base62 hash into first 3 characters and use it as key
- if record already exists for those first 3 characters, use 4 characters
- its generally a hash table backed by sha512-256 with base62 characters
- we use base62 because its more readable than hex
references