Since Elixir is not object oriented, there are no module level variables (“properties”) that you could set like this. A process can keep state which can contain that data, and that you could accomplish with Agent or GenServer, but a single process may (or may not) become a bottleneck for the queries. Another option is to put the data in ETS, perhaps using some caching wrapper. There is also persistent_term which are kind of globals, but writing to them is expensive.
Personally I would think if I really need to do this, as databases should be quite good at checking a unique index already. But if I did need it and was running on a single node, I would use ETS and get the ID from there.
