Rebalancing Shards & Data Migration
Scale a live sharded cluster without downtime: Online data migration, dual-writing, CDC catchup, cutover switching, and shadow validation.
01.Why Shard Rebalancing is the Hardest Distributed Task
As a business expands, existing database shards become overloaded (e.g., 4 shards running at 95% disk capacity). To relieve load, you must add 4 new shards and redistribute 50% of all data across the cluster.
The Production Challenge: How do you move 10 Terabytes of live data across a running cluster handling 50,000 requests/sec with ZERO downtime and ZERO data loss?
A naive offline migration (putting the database in maintenance mode for 8 hours) costs millions of dollars in downtime. Production architectures execute Zero-Downtime Online Migrations.
Zero-Downtime Live Shard Rebalancing & Migration Pipeline 🔄
Zero-Downtime Live Shard Rebalancing & Migration Pipeline 🔄
The 4-stage zero-downtime shard migration framework: Historical Backfill, Real-time CDC streaming, Shadow Validation, and Atomic Cutover.
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