Types of caching: every layer from browser to database
Browser, CDN, reverse proxy, app memory, Redis and database: what each caching layer stores, who shares it, and how one results-day request moves through them.
#system design
7 articles tagged #system design
Articles
Horizontal vs vertical scaling: which should you use?
Scale up or scale out? The trade-offs in cost, limits and downtime, what stateless apps need, and why databases usually grow vertically first, with a worked cost example.
L4 vs L7 load balancers: differences and when to use each
What layer 4 and layer 7 load balancers can see and do, ALB vs NLB on AWS, load balancing algorithms, and a typical layout for a learning platform.
Rate limiting algorithms: token bucket vs leaky bucket
Fixed and sliding windows, token and leaky buckets compared, where to enforce limits, distributed limits with Redis, and how to protect OTP, login and test submission.
Caching strategies: cache-aside, write-through, write-back
Cache-aside, read-through, write-through and write-back compared: how each works, how each fails, and which suits course pages, progress and leaderboards.
Cache invalidation and TTLs: strategies that work
TTLs, event-based deletes and versioned keys: choosing TTLs per data type, purging CDNs, avoiding stale reads after writes, and why eviction isn't invalidation.
Cache stampede and the thundering herd problem
Why one expired key can overload your database, and how locks, request coalescing, probabilistic early refresh, TTL jitter and serving stale data prevent it.
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