Tair (Redis OSS-compatible) offers Serverless KV Redis-compatible instances with automatic scaling and pay-as-you-go billing based on actual usage. During peak hours, instances scale out automatically to ensure business stability without requiring application changes, significantly reducing operational complexity. You are billed only for the resources you actually use, which helps lower costs.
Architecture
Tair Serverless KV Redis-compatible instances use a distributed cluster architecture compatible with Redis Open-Source Edition 6.0. For more information, see Supported commands for Redis-compatible instances. The following figure shows the architecture and describes the components.
Component | Description |
Data shard (Partition) | An instance consists of multiple shards. Data distribution among shards is compatible with Redis Cluster (SLOT). Each data shard uses a high availability (HA) architecture with one master node and multiple secondary nodes deployed on different machines. The number of secondary nodes is at least one. |
High availability (HA) service | If a master node fails, the system automatically switches over to a secondary node (Replica) within 30 seconds to ensure high service availability and data reliability. |
Serverless capabilities
When you create and use Tair Serverless KV Redis-compatible instances, you do not need to configure instance specifications. Instances automatically adapt to your application’s RCU (read operations), WCU (write operations), and storage usage requirements, scaling in or out based on workload. The following concepts are explained:
Storage capacity: Used for data storage, the storage capacity of instances ranges from 0 to 25 TB. Storage capacity scales automatically based on usage. You do not need to pre-provision resources.
RCU (read operation): The smallest unit for a read operation. Each RCU represents one client accessing 4 KB of data. If a single read operation is less than 4 KB, it counts as 1 RCU. If it exceeds 4 KB, round up to the nearest multiple of 4 KB. The formula is: RCU = ⌈Data volume of a single read / 4 KB⌉.
WCU (write operation): The smallest unit for a write operation. Each WCU represents one client writing 512 B of data. If a single write operation is less than 512 B, it counts as 1 WCU. If it exceeds 512 B, round up to the nearest multiple of 512 B. The formula is: WCU = ⌈Data volume of a single write / 512 B⌉.
Initial performance and elastic scaling
A Tair Serverless KV Redis-compatible instance has an initial peak performance (throttling threshold) of 30,000 RCU/s and 20,000 WCU/s. When traffic exceeds 60% of the peak performance, the instance begins to scale out. During scale-out, traffic exceeding the original peak is throttled. After scale-out completes, the new peak performance is twice the original. If traffic continues to exceed 60% of the new peak, the instance scales out again.
A Tair Serverless KV instance guarantees that a scale-out task completes within 30 minutes.
When instance traffic exceeds the rate limiting threshold, excess traffic is rate-limited. By default, requests are queued, consistent with traditional Redis behavior. You can also choose to return an error. For more information, see Client-side rate limiting.
Instance limits
Maximum capacity: 25 TB.
Maximum bandwidth: Maximum inbound and outbound bandwidth is 16 Gbit/s (2 GB/s) each. They are measured independently.
Maximum connections: 400,000.
Maximum throughput: Access performance limit is 7,680,000 RCU/s and 5,120,000 WCU/s.
Hot spot throughput: Request limit for a hot spot key is 30,000 RCU/s and 20,000 WCU/s.
Billing
Tair Serverless KV fees consist of two parts: computing resource fees (RCU/WCU) and storage capacity fees. Tair Serverless KV billing
Get started with Tair Serverless KV Redis-compatible instances
Create and release Tair Serverless KV Redis-compatible instances
Performance monitoring
The performance monitoring feature for Tair Serverless KV instances provides metrics such as usage, traffic, latency, number of requests, key statistics, and hit rate. You can query monitoring data for an instance over a specified time period within the last month to understand its performance and operational status, and troubleshoot performance issues.
Backup and recovery
Tair Serverless KV instances support the following backup and recovery solutions.
Category | Implementation Plan | Description |
Data backup | An instance automatically backs up data based on the default policy. Modify the automatic backup policy or initiate a manual backup as needed. | |
Data restoration | Create a new instance from a specified backup set. The data in the new instance is identical to the data in the backup set. Use this for scenarios such as data restoration, rapid business deployment, or data validation. |
FAQ
Q: Do Tair Serverless KV instances support requesting an Internet endpoint?
A: No. Tair Serverless KV instances support access only over a VPC.
Q: If my instance scales out and then my business traffic quickly drops, do I need to pay for the scaled-up performance?
A: No. Fees are based only on CU and storage usage, not on provisioned backend resources. For example, if an instance’s current performance limit is 30,000 RCU/s and traffic is 200 RCU/s, you are billed only for 200 RCU/s and the current storage capacity. The instance automatically scales in after the request load remains at a low level for a period.
Q: Is data in Tair Serverless KV persistent?
A: Yes. Data in Tair Serverless KV is persisted to disk in real time. Compared with traditional Redis, Tair Serverless KV is more suitable for use as a persistent database.