Design
Distributed Session Store
Design a globally distributed session store that keeps a logged-in user's session valid and consistent across regions and servers.
This is a Low-Level Design (LLD) problem. New to LLD vs HLD? Start here.
01 - Why interviewers ask this
It tests global low-latency reads versus strict security-event consistency — interviewers check if you treat "normal read" and "logout everywhere" as genuinely different consistency problems.
02 - Where this system exists in the real world
You interact with this design every day.
Multi-region web application session management
SSO and identity provider session infrastructure
Global CDN-edge authenticated request validation
03 - What you'll master
Solve this once. Know it forever.
Replicate session data across regions
Design synchronous invalidation for security events
Survive a regional outage without mass logout
04 - What you'll design
6 functional · 3 non-functional requirements.
Create and validate a user session token on login
5 more requirements inside
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05 - Companies that ask this
You may face this exact question in your next interview.
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