Hey all,

I’m trying to build a low-cost website serving a catalogue of items, with standard options of viewing/filtering said items. It is expected that a catalogue itself will be queried often, but rarely updated. It is also a requirement that the website is resilient against DDoS attacks and other script-kiddie-level threats.

Given the requirements (and, let’s be honest, my shallow level of Erlang/Elixir ecosystem knowledge), I was wondering if I can use Agent module to serve as an in-memory cache:

1. Load whole db table into agent’s state as a list (or map of id → item);

2. Whenever a user requests a page, get the table from the Agent’s state, and filter by whichever items are needed;

3. In case of an update - reload table, replace the Agent’s state.

I read about immutability in Elixir and assumed that this would be an improvement compared to making calls to the DB each time, since copied/filtered lists and maps will still point to the same immutable list.

Then I tested both approaches locally by holding down the “F5” button and saw that memory usage goes up either way.

By now, I have read about “share-nothing concurrency” and realized that copying the whole table with the response between processes is probably not the best way to go. And while I can change Agent module to accept a filter and return only requested items (and spawn a bunch of them for good measure) - I wonder if the whole setup even makes sense in practical terms?

Maybe there’s already a module/library that does what I need, or maybe I should stop overthinking, put my server behind DDoS protection by something like Cloudflare, and call it a day?

I would be grateful to hear a hint from someone who has experience in actually deploying something to a live audience.