EasyExperience level: 0-2 years · 3-5 years1 min read

Where do you add caching, and what are the common caching patterns?

Reviewed by Gurusankar M.

Asked inAmazonMicrosoftDeloitte
#caching#cache-aside#write-through#ttl#invalidation
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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.

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Concept Made Simple

Coffee Chat Question

“Where do you add caching, and what are the common caching patterns?”

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Mind Map Answer

Cache-aside
load on miss, app-managed (common)
Write-through
write cache + DB together
Write-behind
write cache, flush to DB async
Always
TTL + eviction (LRU)

Think Beyond the Expected

What If?

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:

  • cache-aside/write-through/behind
  • TTL + eviction
  • invalidation is hard
  • stampede/thundering herd
  • multi-layer caching

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

  1. Cache-aside vs write-through — trade-offs?
  2. How do you keep the cache consistent with the DB?
  3. What is stale-while-revalidate?

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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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