Aha! Senior Front End Engineer interview questions

Recruiter screen ~45 minutes, very detailed and positive discussion. Technical round ~60 minutes, very in depth technical questions. Good conversation. Ultimately turned down for not possessing "really strong algorithmic skills" despite never given the chance to demonstrate in practice and failing to answer one question about creating a performant typeahead for millions of emails in-memory on the client without a debounce. Apparently building typeahead with server-side querying w/ pagination that searches millions of records vs. in-memory hashmap is not an acceptable solution.