Where do you add caching, and what are the common caching patterns?
Reviewed by Gurusankar M.
⚡ Short Answer
Cache at multiple layers (browser/CDN, app, DB). Patterns: cache-aside (app loads on miss, most common), write-through (write cache+DB together), write-behind (async). Always set a TTL and a sensible eviction policy (LRU) — and remember cache invalidation is the hard part.
☕Coffee Chat Question
Concept Made Simple
“Where do you add caching, and what are the common caching patterns?”
🧠Mind Map Answer
Remember It Faster
🔥What If?
Think Beyond the Expected
What is a cache stampede, and how do you prevent it?
When a hot key expires, many requests miss simultaneously and all hit the DB at once (thundering herd). Prevent it with request coalescing (single flight — one loader, others wait), slightly randomized TTLs (jitter), or serving stale-while-revalidate.
😂Real World
Cache-aside with Redis is the default; the classic incidents are stale data (bad invalidation) and cache stampedes on hot keys — solved with TTL jitter and single-flight loading.
🎯Interviewer's Expectation
Keywords they're listening for:
⚠️Common Mistakes
- ✗No TTL (stale forever)
- ✗No stampede protection on hot keys
- ✗Caching data that must be strongly consistent
✅Best Practices
- ✓Cache-aside + TTL with jitter
- ✓Single-flight loading for hot keys
- ✓Plan invalidation explicitly
🔁Follow-up Questions
- 1Cache-aside vs write-through — trade-offs?
- 2How do you keep the cache consistent with the DB?
- 3What is stale-while-revalidate?
🧩Related Technologies
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Plain-language foundations
I'm preparing for a software engineering interview and want to understand this from scratch, as a beginner. Topic: Caching (System Design) Interview question: "Where do you add caching, and what are the common caching patterns?" Please: 1. Explain the core idea in simple, plain language, using an everyday analogy. 2. Define any technical terms you use. 3. Walk through one small, concrete example. 4. Finish with a single sentence I can easily remember. Keep the tone friendly and assume I'm new to this topic.
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