How computers actually work underneath the abstractions.https://penluma.com/https://penluma.com/blog/systems-fundamentals/01-the-big-picture-why-systems-fundamentals-are-durable/https://penluma.com/blog/systems-fundamentals/01-the-big-picture-why-systems-fundamentals-are-durable/Why systems fundamentals like latency, storage, and the four pillars stay useful for decades while frameworks churn - and how to use them to build faster.Sun, 21 Jun 2026 00:00:00 GMTSystems Fundamentalshttps://penluma.com/blog/systems-fundamentals/02-how-a-computer-runs-your-program-cpu-memory-processes-threads/https://penluma.com/blog/systems-fundamentals/02-how-a-computer-runs-your-program-cpu-memory-processes-threads/See how a computer runs your program, from source code to CPU, memory, and threads, and turn performance guesswork into real, confident understanding.Sun, 21 Jun 2026 00:00:00 GMTSystems Fundamentalshttps://penluma.com/blog/systems-fundamentals/03-concurrency-parallelism-doing-many-things-at-once/https://penluma.com/blog/systems-fundamentals/03-concurrency-parallelism-doing-many-things-at-once/Concurrency vs parallelism, explained simply. Learn how computers juggle many tasks, why race conditions happen, and which tool fits I/O vs CPU work.Sun, 21 Jun 2026 00:00:00 GMTSystems Fundamentalshttps://penluma.com/blog/systems-fundamentals/04-databases-i-relational-databases-sql-acid/https://penluma.com/blog/systems-fundamentals/04-databases-i-relational-databases-sql-acid/Learn how relational databases, SQL, and ACID transactions keep your data correct under load - with clear examples, common mistakes, and practical tips.Sun, 21 Jun 2026 00:00:00 GMTSystems Fundamentalshttps://penluma.com/blog/systems-fundamentals/05-databases-ii-how-databases-store-find-data-fast-indexes-b-trees-lsm/https://penluma.com/blog/systems-fundamentals/05-databases-ii-how-databases-store-find-data-fast-indexes-b-trees-lsm/How database indexes find one row in a billion almost instantly. A clear guide to pages, B-trees, LSM-trees, and writing queries that stay fast.Sun, 21 Jun 2026 00:00:00 GMTSystems Fundamentalshttps://penluma.com/blog/systems-fundamentals/06-databases-iii-scaling-up-replication-partitioning-nosql/https://penluma.com/blog/systems-fundamentals/06-databases-iii-scaling-up-replication-partitioning-nosql/Learn how to scale a database past one server with replication, partitioning, and NoSQL - and why reads are easy to scale but writes are genuinely hard.Sun, 21 Jun 2026 00:00:00 GMTSystems Fundamentalshttps://penluma.com/blog/systems-fundamentals/07-networking-i-how-data-travels-ip-tcp-udp-dns/https://penluma.com/blog/systems-fundamentals/07-networking-i-how-data-travels-ip-tcp-udp-dns/A clear, practical guide to how data travels the internet: IP, TCP, UDP, and DNS explained in plain language so you can debug slow, hung, and flaky apps.Sun, 21 Jun 2026 00:00:00 GMTSystems Fundamentalshttps://penluma.com/blog/systems-fundamentals/08-networking-ii-the-web-stack-http-tls-load-balancing-caching/https://penluma.com/blog/systems-fundamentals/08-networking-ii-the-web-stack-http-tls-load-balancing-caching/A clear, practical tour of the web stack: how HTTP requests work, why HTTPS is safe, what load balancers and CDNs do, and how caching makes sites fast.Sun, 21 Jun 2026 00:00:00 GMTSystems Fundamentalshttps://penluma.com/blog/systems-fundamentals/09-distributed-systems-many-computers-working-as-one/https://penluma.com/blog/systems-fundamentals/09-distributed-systems-many-computers-working-as-one/A distributed system makes many computers behave as one. Learn partial failure, CAP, consistency, consensus, and idempotency in plain, practical language.Sun, 21 Jun 2026 00:00:00 GMTSystems Fundamentalshttps://penluma.com/blog/systems-fundamentals/10-data-engineering-moving-shaping-data-at-scale/https://penluma.com/blog/systems-fundamentals/10-data-engineering-moving-shaping-data-at-scale/Learn how data engineering moves and shapes data at scale - OLTP vs OLAP, ETL vs ELT, Kafka, lakehouses, and idempotent pipelines, explained in plain English.Sun, 21 Jun 2026 00:00:00 GMTSystems Fundamentalshttps://penluma.com/blog/systems-fundamentals/11-putting-it-together-designing-a-real-system-trade-offs/https://penluma.com/blog/systems-fundamentals/11-putting-it-together-designing-a-real-system-trade-offs/Learn the repeatable system design process: back-of-envelope estimates, the five universal trade-offs, idempotency, and how to reason about any system.Sun, 21 Jun 2026 00:00:00 GMTSystems Fundamentals