The hard middle of modern engineering - replication, partitioning, and failure.https://penluma.com/https://penluma.com/blog/distributed-systems/11-how-to-use-this-guide/https://penluma.com/blog/distributed-systems/11-how-to-use-this-guide/A distributed system is many computers pretending to be one. Learn what that means, why it's hard, and the six ideas that make it click for beginners.Sun, 21 Jun 2026 00:00:00 GMTDistributed Systemshttps://penluma.com/blog/distributed-systems/12-what-is-a-distributed-system/https://penluma.com/blog/distributed-systems/12-what-is-a-distributed-system/What is a distributed system? Learn how many computers work together to look like one, why we build them, and the core words every developer should know.Sun, 21 Jun 2026 00:00:00 GMTDistributed Systemshttps://penluma.com/blog/distributed-systems/13-why-distributed-systems-are-hard/https://penluma.com/blog/distributed-systems/13-why-distributed-systems-are-hard/Why distributed systems are hard: partial failure, unreliable networks, no shared clock, plus the timeouts, retries, and idempotency that save you.Sun, 21 Jun 2026 00:00:00 GMTDistributed Systemshttps://penluma.com/blog/distributed-systems/14-time-clocks-the-ordering-of-events/https://penluma.com/blog/distributed-systems/14-time-clocks-the-ordering-of-events/Wall-clock timestamps lie across machines. See how Lamport logical clocks and the happens-before relation order events in distributed systems, no shared clock.Sun, 21 Jun 2026 00:00:00 GMTDistributed Systemshttps://penluma.com/blog/distributed-systems/15-vector-clocks-causality/https://penluma.com/blog/distributed-systems/15-vector-clocks-causality/Learn how vector clocks detect causality and concurrent writes in distributed systems, the trick behind Amazon Dynamo conflict detection and database siblings.Sun, 21 Jun 2026 00:00:00 GMTDistributed Systemshttps://penluma.com/blog/distributed-systems/16-the-cap-theorem-and-pacelc/https://penluma.com/blog/distributed-systems/16-the-cap-theorem-and-pacelc/A plain-English guide to the CAP theorem and PACELC: what consistency, availability, and partition tolerance really mean, and how to choose CP vs AP databases.Sun, 21 Jun 2026 00:00:00 GMTDistributed Systemshttps://penluma.com/blog/distributed-systems/17-consistency-models/https://penluma.com/blog/distributed-systems/17-consistency-models/A plain-English guide to consistency models in distributed systems, from linearizability to eventual consistency, and how to pick the right one per data type.Sun, 21 Jun 2026 00:00:00 GMTDistributed Systemshttps://penluma.com/blog/distributed-systems/18-glossary-of-terms/https://penluma.com/blog/distributed-systems/18-glossary-of-terms/A plain-English distributed systems glossary covering CAP, consistency, consensus, clocks, and more. Learn the 40 core terms without the academic jargon.Sun, 21 Jun 2026 00:00:00 GMTDistributed Systemshttps://penluma.com/blog/distributed-systems/19-frequently-asked-questions/https://penluma.com/blog/distributed-systems/19-frequently-asked-questions/Plain-language answers to the distributed systems questions that trip people up: clocks, CAP, consistency, quorums, and why the network keeps lying to you.Sun, 21 Jun 2026 00:00:00 GMTDistributed Systemshttps://penluma.com/blog/distributed-systems/20-revision-cheat-sheet/https://penluma.com/blog/distributed-systems/20-revision-cheat-sheet/A plain-English distributed systems cheat sheet: the 8 fallacies, CAP vs PACELC, logical clocks, and consistency models you can remember under pressure.Sun, 21 Jun 2026 00:00:00 GMTDistributed Systemshttps://penluma.com/blog/distributed-systems/01-how-to-use-this-guide/https://penluma.com/blog/distributed-systems/01-how-to-use-this-guide/Consensus is how separate computers agree on one decision even when some crash. Here's why it's the hardest problem in distributed systems, in plain English.Sun, 21 Jun 2026 00:00:00 GMTDistributed Systemshttps://penluma.com/blog/distributed-systems/02-the-consensus-problem/https://penluma.com/blog/distributed-systems/02-the-consensus-problem/The consensus problem is why distributed databases never lose your data. Learn how machines agree on a single value despite crashes, delays, and lost messages.Sun, 21 Jun 2026 00:00:00 GMTDistributed Systemshttps://penluma.com/blog/distributed-systems/03-replicated-state-machines-the-log/https://penluma.com/blog/distributed-systems/03-replicated-state-machines-the-log/Learn how replicated state machines and the log let Raft, Paxos, and etcd keep database copies identical across crashes, lost messages, and no global clock.Sun, 21 Jun 2026 00:00:00 GMTDistributed Systemshttps://penluma.com/blog/distributed-systems/04-raft-leader-election/https://penluma.com/blog/distributed-systems/04-raft-leader-election/Learn how Raft leader election works: terms, heartbeats, election timeouts, and majority voting that keep a server cluster agreeing without a single boss.Sun, 21 Jun 2026 00:00:00 GMTDistributed Systemshttps://penluma.com/blog/distributed-systems/05-raft-log-replication-safety-membership/https://penluma.com/blog/distributed-systems/05-raft-log-replication-safety-membership/A clear, plain-English guide to Raft log replication, the commit majority rule, the Figure-8 safety bug, cluster membership changes, and snapshotting.Sun, 21 Jun 2026 00:00:00 GMTDistributed Systemshttps://penluma.com/blog/distributed-systems/06-paxos-the-original-consensus-algorithm/https://penluma.com/blog/distributed-systems/06-paxos-the-original-consensus-algorithm/Paxos is the consensus algorithm behind modern distributed systems. Learn how unreliable machines agree on one value, in plain English with clear examples.Sun, 21 Jun 2026 00:00:00 GMTDistributed Systemshttps://penluma.com/blog/distributed-systems/07-multi-paxos-raft-vs-paxos-the-real-world/https://penluma.com/blog/distributed-systems/07-multi-paxos-raft-vs-paxos-the-real-world/Raft vs Paxos explained in plain language: how Multi-Paxos, Raft, and real systems like etcd and Spanner agree on a replicated log, and when you need it.Sun, 21 Jun 2026 00:00:00 GMTDistributed Systemshttps://penluma.com/blog/distributed-systems/08-glossary-of-terms/https://penluma.com/blog/distributed-systems/08-glossary-of-terms/A plain-English glossary of distributed consensus terms. Understand Raft, Paxos, quorums, terms, leaders, safety, and liveness without the academic jargon.Sun, 21 Jun 2026 00:00:00 GMTDistributed Systemshttps://penluma.com/blog/distributed-systems/09-frequently-asked-questions/https://penluma.com/blog/distributed-systems/09-frequently-asked-questions/Raft vs Paxos, quorums, split-brain, and partitions explained in plain language. The consensus answers engineers actually search for, without the math.Sun, 21 Jun 2026 00:00:00 GMTDistributed Systemshttps://penluma.com/blog/distributed-systems/10-revision-cheat-sheet/https://penluma.com/blog/distributed-systems/10-revision-cheat-sheet/A clear guide to distributed consensus: how Raft and Paxos keep replicas in sync with majority quorums, why you need 3 or 5 nodes, and how to avoid split-brain.Sun, 21 Jun 2026 00:00:00 GMTDistributed Systems