I started with DNS and HTTP basics, which was fine, but I underestimated how much they wanted on the redirect mechanics specifically.
Start by clarifying the scope and assumptions (e.g., scale, read-heavy workload, caching) before diving into the end-to-end flow. Then walk through the request lifecycle from DNS resolution to the final redirect, highlighting key components like load balancers, caching layers, and the database. Emphasize trade-offs and how you would design for high availability and low latency, especially at LinkedIn's scale.
Pro tip: Mention that you would use a distributed cache (like Redis) with a read-through pattern and a 301 vs 302 redirect decision based on analytics needs—this shows you understand both performance and business trade-offs.
Ask about scale (e.g., millions of redirects per day), read/write ratio, latency requirements, and whether analytics are needed. State assumptions to guide your design.
Describe the client-side steps: DNS lookup, TCP handshake, HTTP request to the short URL domain. Then explain the server-side: load balancer, application server, cache lookup, database fallback, and HTTP redirect response.
Explain how the short code is mapped to the long URL: database schema (e.g., key-value store), caching strategy (e.g., Redis with TTL), and how to handle cache misses. Discuss redirect types (301 vs 302) and their implications.
Discuss how to scale reads (replication, sharding, CDN for static assets), handle hot keys, and ensure high availability. Mention trade-offs like consistency vs. latency, and cost vs. performance.
Briefly mention monitoring (latency, error rates), analytics logging, and edge cases like expired links, malicious URLs, or custom aliases.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.