A 20-module, staff-level curriculum: from back-of-the-envelope estimation to consensus, consistency models, and real-world case studies.https://penluma.com/https://penluma.com/blog/system-design/00-index-learning-roadmap/https://penluma.com/blog/system-design/00-index-learning-roadmap/A clear 20-step roadmap to learn system design from CRUD apps to distributed systems - what to study, in what order, and how to actually make it stick.Mon, 15 Jun 2026 00:00:00 GMTSystem Designhttps://penluma.com/blog/system-design/01-foundations-and-estimation/https://penluma.com/blog/system-design/01-foundations-and-estimation/Learn back-of-the-envelope estimation to size any system for millions of users in ten minutes. QPS, storage, Little's Law, and percentiles, explained simply.Mon, 15 Jun 2026 00:00:00 GMTSystem Designhttps://penluma.com/blog/system-design/02-networking-and-protocols/https://penluma.com/blog/system-design/02-networking-and-protocols/Learn how networking and protocols like TCP, TLS, and HTTP/3 add round-trips that make sites slow - and the simple fixes that make pages feel instant.Mon, 15 Jun 2026 00:00:00 GMTSystem Designhttps://penluma.com/blog/system-design/03-api-design-and-communication/https://penluma.com/blog/system-design/03-api-design-and-communication/Learn API design that lasts: REST vs GraphQL vs gRPC, idempotency keys, cursor pagination, versioning, and webhooks that never double-charge a customer.Mon, 15 Jun 2026 00:00:00 GMTSystem Designhttps://penluma.com/blog/system-design/04-databases-internals/https://penluma.com/blog/system-design/04-databases-internals/A clear guide to database internals: how storage engines, indexes, transactions, and MVCC really work, and why understanding them makes your queries fast.Mon, 15 Jun 2026 00:00:00 GMTSystem Designhttps://penluma.com/blog/system-design/05-data-modeling-sql-nosql/https://penluma.com/blog/system-design/05-data-modeling-sql-nosql/A practical guide to SQL vs NoSQL data modeling: when joins break, how to pick a partition key, single-table DynamoDB design, and polyglot persistence.Mon, 15 Jun 2026 00:00:00 GMTSystem Designhttps://penluma.com/blog/system-design/06-caching-deep/https://penluma.com/blog/system-design/06-caching-deep/A practical caching deep dive: how cache hit ratio protects your database, the read/write patterns to use, and the four failures that turn caches into outages.Mon, 15 Jun 2026 00:00:00 GMTSystem Designhttps://penluma.com/blog/system-design/07-load-balancing-and-scaling/https://penluma.com/blog/system-design/07-load-balancing-and-scaling/Learn how load balancing, stateless design, and autoscaling let one web app grow into a fleet that handles huge traffic spikes without crashing.Mon, 15 Jun 2026 00:00:00 GMTSystem Designhttps://penluma.com/blog/system-design/08-replication-and-partitioning/https://penluma.com/blog/system-design/08-replication-and-partitioning/Learn how replication keeps copies of your data alive and how partitioning (sharding) splits huge datasets across machines, plus the failures that bite at 3am.Mon, 15 Jun 2026 00:00:00 GMTSystem Designhttps://penluma.com/blog/system-design/09-cap-pacelc-consistency-models/https://penluma.com/blog/system-design/09-cap-pacelc-consistency-models/CAP theorem and PACELC made clear. Learn what your database really guarantees during a network partition and how to choose the right consistency model.Mon, 15 Jun 2026 00:00:00 GMTSystem Designhttps://penluma.com/blog/system-design/10-consensus-and-coordination/https://penluma.com/blog/system-design/10-consensus-and-coordination/Learn how distributed systems reach agreement when nodes crash or stall - Paxos, Raft, distributed locks, fencing tokens, and why consensus is hard.Mon, 15 Jun 2026 00:00:00 GMTSystem Designhttps://penluma.com/blog/system-design/11-distributed-transactions-and-idempotency/https://penluma.com/blog/system-design/11-distributed-transactions-and-idempotency/Distributed transactions break the moment data crosses two services. See how sagas, the transactional outbox, and idempotency keys keep systems correct.Mon, 15 Jun 2026 00:00:00 GMTSystem Designhttps://penluma.com/blog/system-design/12-messaging-and-event-driven/https://penluma.com/blog/system-design/12-messaging-and-event-driven/Message queues vs Kafka, delivery guarantees, ordering, and dead-letter queues, explained in plain language so you can design event-driven systems.Mon, 15 Jun 2026 00:00:00 GMTSystem Designhttps://penluma.com/blog/system-design/13-event-sourcing-and-cqrs/https://penluma.com/blog/system-design/13-event-sourcing-and-cqrs/Event sourcing stores every change as an immutable fact, and CQRS splits reads from writes. Learn how both work, when they pay off, and when they're overkill.Mon, 15 Jun 2026 00:00:00 GMTSystem Designhttps://penluma.com/blog/system-design/14-stream-processing-realtime/https://penluma.com/blog/system-design/14-stream-processing-realtime/Learn how stream processing reacts to data the instant it arrives. Event time, watermarks, exactly-once, Lambda vs Kappa, and real pipelines made simple.Mon, 15 Jun 2026 00:00:00 GMTSystem Designhttps://penluma.com/blog/system-design/15-probabilistic-structures-and-algorithms/https://penluma.com/blog/system-design/15-probabilistic-structures-and-algorithms/Probabilistic data structures like Bloom filters and HyperLogLog count billions of items in kilobytes, trading a little accuracy for huge memory savings.Mon, 15 Jun 2026 00:00:00 GMTSystem Designhttps://penluma.com/blog/system-design/16-rate-limiting-and-resiliency/https://penluma.com/blog/system-design/16-rate-limiting-and-resiliency/Learn rate limiting and resiliency patterns that keep systems alive under load: token buckets, circuit breakers, retries with jitter, bulkheads, and more.Mon, 15 Jun 2026 00:00:00 GMTSystem Designhttps://penluma.com/blog/system-design/17-observability-and-operations/https://penluma.com/blog/system-design/17-observability-and-operations/Learn observability the practical way: metrics, logs, traces, SLIs and SLOs, error budgets, smart alerting, and deploys that recover without a second outage.Mon, 15 Jun 2026 00:00:00 GMTSystem Designhttps://penluma.com/blog/system-design/18-architecture-patterns-microservices/https://penluma.com/blog/system-design/18-architecture-patterns-microservices/A clear guide to monolith vs microservices: how to find real service boundaries, migrate safely with strangler-fig, and cap blast radius with cells.Mon, 15 Jun 2026 00:00:00 GMTSystem Designhttps://penluma.com/blog/system-design/19-specialized-systems-search-geo-timeseries/https://penluma.com/blog/system-design/19-specialized-systems-search-geo-timeseries/Learn when a standard database can't answer your query, and which specialized database to reach for instead: search, geospatial, time-series, or analytics.Mon, 15 Jun 2026 00:00:00 GMTSystem Designhttps://penluma.com/blog/system-design/20-case-studies-and-interview-framework/https://penluma.com/blog/system-design/20-case-studies-and-interview-framework/A repeatable 7-step framework for the system design interview, plus 10 worked case studies from URL shorteners to payments. Walk in calm, control the room.Mon, 15 Jun 2026 00:00:00 GMTSystem Design