Story

hi! i want to build an a/b testing tool, but i'm struggling to learn how to approach building some aspects.

for clarification, i'm not looking for a/b testing tools. rather, i'm looking for resources on how I can build these types of a/b tools myself. i have a high level overview of the data flow and architecture that i know my product should have. i need to hash each user_id to ensure each user consistently gets the same version, and also need to ensure that each version is split evenly among the entire userbase. then i should store this user_id-version mapping for quick lookup later. but i'm stumped when it comes to this:

- how do i know which hashing algorithm to use to ensure that each version is split evenly among the userbase? - is it better to build and run this hashing and allocation in-house or are there external services that help with this?