In reality, the article is about correctly caching a path:policy mapping while working within the limitations of eBPF and Linux filesystem semantics. If you read the article in that context rather than wondering 'what is new and interesting about memoization in eBPF?' it's a lot more interesting.

I probably would have titled this 'Calculating cache keys for filesystem paths in eBPF' or something, since that's the cool and interesting problem that was solved.