I've seen this question before so I wasn't panicking, but the scope they wanted was bigger than I expected.
Structure your answer as a chronological narrative from the browser to the server and back, covering each layer of the stack in order. Balance breadth (mentioning all major components) with depth (explaining key protocols and trade-offs) to show you understand both the big picture and critical details. Conclude by tying it back to system design principles like caching, scalability, and latency.
Pro tip: Don't just list technologies—explain why each step exists and what could go wrong (e.g., DNS caching, TCP handshake latency, TLS overhead, CDN edge selection). This demonstrates engineering maturity and an understanding of trade-offs.
Start with the user typing the URL: browser checks cache, then resolves the domain via DNS (recursive resolver, root, TLD, authoritative). Mention DNS caching at multiple levels and how it affects latency.
Explain the TCP three-way handshake and TLS handshake (if HTTPS), including certificate validation and session resumption. Highlight the latency cost and optimizations like TCP Fast Open or TLS 1.3.
Describe how the HTTP request is sent, possibly hitting a CDN edge server first. Explain how CDNs cache content and how load balancers distribute traffic to backend servers, including health checks and algorithms.
Cover what happens on the server: request routing, application logic, database queries, and response generation. Mention caching layers (e.g., Redis) and how responses are sent back through the load balancer and CDN.
Explain how the browser parses HTML, builds the DOM/CSSOM, executes JavaScript, and renders the page. Mention critical rendering path, resource loading, and potential optimizations like lazy loading.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.