DATABASE REPLICATION.

Your database will crash. It's not a matter of if it will crash, it's when. So here's my question: is your system designed to survive it? *One database. One crash. Total downtime. * That's the risk you take without replication. Here's how serious systems avoid it: a single Primary absorbs all writes while multiple Replicas serve reads in parallel. The result is faster performance, fault tolerance, and no single point of failure. When the primary goes down, a replica steps up automatically, users never feel a thing. This is the backbone of every 24/7 application you've ever used. If backend or system designs are in your future, get comfortable with this concept now. The tricky part is replication lag. Since syncing happens asynchronously, a replica might be milliseconds (or more) behind the primary database. If a user writes something and immediately reads it back from a replica, they might not see their own write yet. Synchronous replication guarantees zero data loss but slows down eve