Read Replicas and Write Splitting
Scaling reads with replicas, understanding replication lag, and routing connections intelligently.
Your application is growing. Queries are getting slower, but not because the queries are bad — you've already optimized indexes, fixed N+1 problems, and added caching. The problem is volume. Ten thousand users hitting the database simultaneously, and every query contends for the same resources.
Here's the insight: most applications are read-heavy. For every write (creating an order, updating a profile), there are 10 to 100 reads (loading dashboards, listing products, checking permissions). If you could separate the read workload from the write workload, you could scale them independently.
That's exactly what read replicas do.
How Replication Works
A read replica is a copy of your primary database that stays in sync through continuous replication. The primary handles all
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