Q1. What are the Redis data structures and what is each used for?
Redis exposes several core data types, each with tailored commands. - Strings: counters, cached serialized objects and rate limiters using INCR and SETEX. - Hashes: objec...
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Q2. What is caching and why is it used?
Caching stores a copy of data in a faster or closer tier so future reads avoid the slower origin. It reduces latency, increases throughput, lowers load and cost on databa...
Q3. How would you design a URL shortener like bit.ly?
Requirements: shorten a long URL, redirect quickly, handle ~100M new links per day with a 100:1 read-to-write ratio. API: POST /api/links {longUrl} -> {shortUrl}; GET /{c...
Q4. Explain Docker layers and how caching works.
A Docker image is a stack of read-only layers. Each Dockerfile instruction creates a layer, and layers are shared between images and cached. Build cache: - Docker checks ...
Q5. Explain caching strategies and common failure modes.
Strategies: - Cache-aside (lazy loading): app checks cache, on miss reads DB and populates. Most common. - Read-through: cache library fetches on miss. - Write-through: w...
Q6. Describe how DNS resolution works.
DNS maps names to records, most importantly A and AAAA addresses, plus CNAME, MX, TXT and NS. A lookup can walk several servers, but caching means most lookups stop early...
Q7. How does data fetching and caching work in the App Router?
You fetch inside async Server Components using the extended fetch: ```ts const res = await fetch('https://api.example.com/posts', { next: { revalidate: 60, tags: ['posts'...
Q8. How does code splitting produce chunks?
Code splitting divides the bundle so the browser downloads only what a route or interaction needs. Bundlers detect dynamic import() and create a separate chunk for that m...
Q9. How do HTTP caching and CDNs improve performance?
Caching avoids re-downloading assets and is one of the cheapest performance wins. Use content-hashed filenames with a long Cache-Control: public, max-age=31536000, immuta...
Q10. How do you prevent a cache stampede or thundering herd?
A stampede happens when a popular key expires and many clients simultaneously hit the database to rebuild it. Several mitigations exist. - Locking or mutex: only the firs...