Mock interview: phone OTP sign-in and sessions at Paisly
A full 45-minute model interview: Siddharth splits sign-in into its four paths, finds that the Diwali sale needs both SMS providers live, stores the OTP as an HMAC with capped guesses, uses signed tokens with a pushed deny list for lost phones, fails over on delivery receipts, fixes a replica-lag bug and a hot celebrity number, and pushes back on 7-day sessions with numbers.
01 · The call starts
NHNandini HegdePrincipal Engineer, Identity and Access
SRSiddharth RaneCandidate
Mock interview: phone OTP sign-in and sessions at Paisly.
A 45-minute design round
Nandini Hegde: Hi Siddharth, I'm Nandini Hegde, Principal Engineer on the Identity and Access team at Paisly.
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