Engineering at Scale

Engineering at Scale

Engineering at Scale 8 min read

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.

PS Prajjwal Sinha Aug 17, 2026

Engineering at Scale

Engineering at Scale 9 min read

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.

PS Prajjwal Sinha Aug 13, 2026

Engineering at Scale

Engineering at Scale 8 min read

WebSocket scaling for live classes, chat and polls

How to scale WebSockets: connections per server, load balancing long-lived connections, Redis pub/sub fan-out, reconnect storms, and when SSE or polling is simpler.

PS Prajjwal Sinha Aug 10, 2026

Engineering at Scale

Engineering at Scale 10 min read

Cache-Control headers explained: no-cache, no-store, max-age

What each Cache-Control directive does, no-cache vs no-store, ETags and revalidation, and ready-to-use headers for static files, HTML, APIs and HLS video.

PS Prajjwal Sinha Aug 7, 2026

Engineering at Scale

Engineering at Scale 10 min read

CDN caching: how edge caches work, with Cloudflare rules

How edge caches decide hits and misses, what Cloudflare caches by default, cache rules for HTML, APIs and HLS, measuring hit ratio, and purging safely.

PS Prajjwal Sinha Aug 4, 2026

Engineering at Scale

Engineering at Scale 8 min read

Nginx proxy_cache and microcaching: a practical guide

Set up Nginx proxy_cache, microcache dynamic pages for one second, bypass logged-in users, and stop pile-ups with cache locks and stale-while-updating.

PS Prajjwal Sinha Aug 1, 2026

Engineering at Scale

Engineering at Scale 8 min read

Django caching: per-view, fragment and low-level caching

Pick a Django cache backend, use cache_page, template fragment caching and the low-level API safely, and invalidate with signals and versioned keys.

PS Prajjwal Sinha Jul 29, 2026

Engineering at Scale

Engineering at Scale 9 min read

Redis cache: how it works, and Redis vs Memcached

Why Redis is fast, how TTLs and eviction policies work, how to size memory, when persistence matters for a cache, and how Redis compares with Memcached.

PS Prajjwal Sinha Jul 26, 2026

Engineering at Scale

Engineering at Scale 8 min read

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.

PS Prajjwal Sinha Jul 23, 2026

Engineering at Scale

Engineering at Scale 7 min read

Postgres materialized views: query-level caching

Precompute leaderboards and reports inside PostgreSQL: create and index materialized views, refresh them concurrently, schedule refreshes, and know the alternatives.

PS Prajjwal Sinha Jul 20, 2026

Engineering at Scale

Engineering at Scale 9 min read

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.

PS Prajjwal Sinha Jul 17, 2026

Engineering at Scale

Engineering at Scale 8 min read

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.

PS Prajjwal Sinha Jul 14, 2026