This topic describes the billable items of Realtime Compute.

The basic billing unit of Realtime Compute is compute unit (CU), which indicates computing resources. One CU is equal to 1 CPU core and 4 GB memory. The number of CUs determines the CPU computing capability of the underlying system of Realtime Compute.

The number of CUs consumed in a Realtime Compute job depends on the queries per second (QPS) of the input data stream of the job, computing complexity, and distribution of the input data. To estimate the processing capability of one CU in Realtime Compute, select one of the following methods based on the operation complexity:
  • For simple operations such as single-stream filtering and string conversion, one CU can process 10,000 data records per second.
  • For complex operations such as operations that use a JOIN clause, GROUP BY clause, or window function, one CU can process 1,000 to 5,000 data records per second.
You can estimate the number of resources that you need to purchase based on your business scale and the preceding computing capability.
  • The preceding computing capability estimate refers only to the internal processing capability of Realtime Compute. The external data read and write capability is not included. The external data read and write efficiency may affect the estimation of the computing capability of Realtime Compute.
    • If Realtime Compute needs to read data from Log Service but the query quota of Log Service is limited, the overall computing capability of Realtime Compute is limited to the capability allowed by Log Service.
    • If there are limits on the number of connections or transactions per second (TPS) of the ApsaraDB for RDS database that Realtime Compute references, the throughput of Realtime Compute is limited by the throttling of the ApsaraDB for RDS database.
  • If you use window functions in a Realtime Compute job, the number of CUs consumed in the job is greater than that consumed in a simple job. We recommend that you purchase at least four CUs for such a job.