Cosmos DB 429: Request rate is large (TooManyRequests, RU/s exceeded)
The container or database used more Request Units per second than provisioned, so Cosmos DB throttled requests.
Seen on:
Azure
Meaning
Every operation costs RUs. Hot partition keys, cross-partition queries, large documents or bulk imports exceed provisioned/autoscale RU/s. SDKs retry with x-ms-retry-after-ms but can give up.
Common causes
- Provisioned RU/s too low
- Hot partition key concentrating load
- Expensive queries (cross-partition, no index)
- Bulk ingestion without throttling
⚡ Quick fix
- Increase RU/s or enable autoscale
- Choose a better partition key / spread load
- Optimise queries and indexing; use bulk executor with backoff
Detailed fix by platform
Azure CLI
az cosmosdb sql container throughput update -a cosmos-app -g rg -d appdb -n orders --max-throughput 4000
How to diagnose
- Metrics — Normalized RU consumption per partition
- Queries — RU charge (x-ms-request-charge)
- Keys — Hot partitions
🔧 Still not fixed?
Many errors look alike. If the steps above didn’t solve it, one of these is probably what you’re facing:
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Other ways to find it
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Last updated 7 Oct 2026