MongoDB High Availability: Building a 3-Node Replica Set from Scratch

Watch the first episode from this series with Diego: https://www.youtube.com/watch?v=kSSO_IE2H08 Ensuring database reliability is critical for any application. This tutorial walks through the transition from a single MongoDB node to a robust, three-node replica set using Docker Compose. Learn how to configure high availability, initialize the replica set, and understand the internal "election" process that keeps your data accessible even if a primary node fails. The video also covers the MongoDB oplog, eventual consistency, and how to properly structure your connection strings to ensure your application remains connected to the cluster during a failover. See what Atlas is capable of for free: https://mdb.link/YT-Atlas-Register 00:00:00 Introduction to MongoDB Replica Sets 00:00:21 The Risks of a Single-Node Database 00:02:49 Environment Cleanup & Docker Preparation 00:03:39 Configuring the Primary Node in Docker Compose 00:06:17 Scaling to a 3-Node Cluster Configuration 00:07:43 Deploying the Containers 00:08:18 Initializing the Replica Set with Mongosh 00:10:56 How High Availability & Elections Work 00:13:57 Verifying Data Persistence on the Host 00:14:42 Managing Clusters with MongoDB Compass 00:15:35 Testing Failover: Forcing a Node Step Down 00:17:39 Updating Connection Strings for Cluster Support 00:21:05 Behind the Scenes: The MongoDB Oplog 00:24:14 Read/Write Preferences & Eventual Consistency 00:27:32 Future Proofing: Backups vs. Sharding Resources: MongoDB main YouTube channel: https://www.youtube.com/@MongoDB Website: https://mdb.link/MongoDBYT LinkedIn: https://www.linkedin.com/company/mongodbinc MongoDB Developer Blog: https://mdb.link/developerblogYT