System Design: Consensus & Paxos, Raft & Leader Election Explained

Consensus in System Design explained from first principles — including Paxos, Raft, Leader Election, and why consensus matters in distributed databases. If you are learning System Design or Distributed Systems, understanding consensus is essential for understanding how multiple machines can agree on the same state even when servers fail, messages are delayed, or the network is partitioned. In this video, we break down the core idea of distributed consensus and connect it to real-world system design. 🚀 WHAT YOU'LL LEARN • What is Consensus in Distributed Systems? • Why do distributed systems need consensus? • What are Paxos and Raft? • Paxos explained conceptually • Raft explained conceptually • What is Leader Election? • How does a distributed system elect a leader? • What happens when the leader fails? • Why do distributed databases need consensus? • How consensus helps replicated systems maintain consistent state • How consensus connects to System Design interviews • Why consensus is important for fault-tolerant distributed systems • How consensus relates to replication, quorum, and distributed databases 🧠 CONSENSUS IN SYSTEM DESIGN When multiple machines need to agree on an important decision, simply replicating data is not enough. Distributed systems need mechanisms that allow nodes to agree on things such as: → Who is the current leader? → What is the correct order of operations? → Which data has been committed? → What should happen when a server fails? → How can replicas maintain a consistent state? This is where distributed consensus becomes important. 📚 PAXOS & RAFT Paxos and Raft are two important consensus algorithms to understand when learning distributed systems. Rather than getting lost in the implementation details, this video focuses on building an intuitive understanding of the concepts behind them and why they matter in system design. 👑 LEADER ELECTION Leader election is one of the most important ideas behind many distributed systems. We'll understand: • Followers • Candidates • Leaders • Voting • Majority / Quorum • Leader failure • Electing a new leader • Why having multiple conflicting leaders can be dangerous 🗄️ CONSENSUS & DISTRIBUTED DATABASES Consensus is closely connected to replicated state machines, distributed databases, coordination systems, and fault-tolerant architectures. Understanding consensus helps you reason about systems such as distributed databases and other infrastructure where multiple nodes must maintain a consistent view of system state. 🎯 WHY THIS MATTERS FOR SYSTEM DESIGN If you're preparing for System Design interviews, backend engineering roles, or learning Distributed Systems from scratch, consensus is one of the foundational concepts worth understanding. This video is part of my journey of learning backend engineering and system design by building and understanding concepts from first principles. Topics covered: Consensus Distributed Consensus Paxos Paxos Algorithm Raft Raft Consensus Algorithm Raft Algorithm Leader Election Distributed Systems System Design System Design Interview Distributed Databases Database Replication Fault Tolerance Quorum Replicated State Machines High Availability Backend Engineering Scalable Systems 💻 CONNECT WITH ME X / Twitter: https://x.com/aadityakumarsa LinkedIn:   / aaditya-sah-516178308   If you're learning backend engineering, distributed systems, and system design, follow along as we build and understand these concepts step by step. #SystemDesign #DistributedSystems #Consensus #Paxos #Raft #LeaderElection #BackendEngineering #DistributedDatabase #SoftwareEngineering #SystemDesignInterview