--- title: "Interviewer Notes - 1" description: "A practical front-end interviewer's notebook covering warm-up questions, technical topics (Session/Cookie, performance, SEO, testing, DevOps), and JavaScript/CSS/Vue coding challenges — useful whether you're preparing to interview or conducting one." canonical_url: "https://blog.markkulab.net/en/post/front-end-interview" author: "Mark Ku" author_url: "https://blog.markkulab.net/en/author/mark-ku" site: "Mark Ku's Tech Notes" date_published: "2020-07-24 15:01:35 +0300" category: "Frontend" tags: ["interview", "frontend", "javascript", "vue", "css", "devops"] language: "en" license: "CC BY 4.0" license_url: "https://creativecommons.org/licenses/by/4.0/" attribution: "when reusing or quoting, credit the author and link back to the original" --- # Interviewer Notes - 1 ## Front-end-interview ## Opening - Please introduce yourself from a technical perspective — walk me through what you've worked on over the past few years. Keep it within five minutes. ## Warm-up - Interviewer self-introduction: role overview, responsibilities, and what we're looking for in this position - Ask the candidate to highlight relevant experience based on what was just described - What was your role at your last job? Can you walk me through a project you're most proud of? - What are your expectations? What's the one thing you most want to learn this year? - Have you been following any new technologies lately? Any takeaways? Have you tried them out? Any open-source work to share? - Do you enjoy writing code? What aspect of coding do you find most interesting? - Whiteboard: write a string reversal function - What did you learn from your previous job? - Have you been reading any programming-related books recently? ## What to observe - Attitude - Genuine interest in front-end development - Willingness to learn new things - Culture and communication fit with the team - Whether foundational skills are solid enough ## Technical Questions (target: 2+ years of experience) ### Session / Cookie - After a user logs in on one page, how does the next page know they're authenticated? - Where do you typically store frequently used user data? ### Performance - Have you implemented caching before? When should caching be used? - How do you optimize a website's static assets? How do you bundle them — into how many files, and how do you decide? How do you debug after bundling? - If a static file is cached and a new version is released, how do you force an update? Version numbers in filenames? Any other approaches? - Have you used a CDN before? - Walk me through a few techniques you've used to speed up page load times. - An article-listing website needs to frequently query 50+ posts for the homepage — how would you handle that? - Have you ever dealt with complaints about slow page loading? What was the situation and how did you resolve it? Where do you look first? - You have around 500 records to display paginated on a web page — how would you approach it? What about 50,000 records? - When do you populate an in-memory cache? If it sacrifices startup time and slows down development, how do you handle that? - When there are multiple application servers, how do you handle caching? If the cache lives in a database, who is responsible for updating it? - Have you ever encountered slow database queries in production? How would you investigate? How do you determine whether the bottleneck is network, query, or something else? ### SEO - How does fetching data via Ajax affect SEO? - What are the key factors in SEO? What optimizations have you implemented? What tools have you used? Meta tags, keywords, title, responsive design, content quality, server-side rendering, routing, URL rewrite, canonical URL, user experience, robots.txt - When a site is under maintenance, crawlers may still visit — how do you handle that? ### Testing - What languages/frameworks have you written tests in? - If the function you're testing calls `updateDB`, how do you handle that in your test? - What is TDD? Does it make a practical difference compared to writing tests after the code? - Have you used any design patterns specifically to support TDD? - What about BDD? - What end-to-end testing tools have you used? ### Data Analysis - What is the purpose of using GA? Have you collected custom events with GA? How? - Have you used the ELK Stack? ### Design - If you needed to log the input and output of every request, how would you implement that? - When would you use an interface? ### DevOps - What is DevOps? - Have you used any CI/CD tools? What are the benefits? - Have you used cloud services? What are the advantages? ### Debugging - If a user's order data disappeared on the frontend, where would you start looking? - How would you query logs across 10 servers? ### Advanced - Three clients — a website, a mobile browser, and a mobile app — all consume the same API. The mobile app gets a new version that requires a different data format for one field. How do you handle this without breaking the others? - Have you built a real-time application? If a backend service needs to push a message to a specific user, Andy, how would you route it? How do you know which connection ID maps to Andy? If the mapping is stored per-server and there are multiple servers, how do you resolve the mapping? ### Coding #### JavaScript - What is the difference between placing `