Timeouts and Retries for Latency-Sensitive Applications
There are certain situations where an application receives a response from Amazon S3 indicating that a retry is necessary. Amazon S3 maps bucket and object names to the object data associated with them. If an application generates high request rates (typically sustained rates of over 5,000 requests per second to a small number of objects), it might receive HTTP 503 slowdown responses. If these errors occur, each AWS SDK implements automatic retry logic using exponential backoff. If you are not using an AWS SDK, you should implement retry logic when receiving the HTTP 503 error. For information about back-off techniques, see Error Retries and Exponential Backoff in AWS in the Amazon Web Services General Reference.
Amazon S3 automatically scales in response to sustained new request rates, dynamically optimizing performance. While Amazon S3 is internally optimizing for a new request rate, you will receive HTTP 503 request responses temporarily until the optimization completes. After Amazon S3 internally optimizes performance for the new request rate, all requests are generally served without retries.
For latency-sensitive applications, Amazon S3 advises tracking and aggressively retrying slower operations. When you retry a request, we recommend using a new connection to Amazon S3 and performing a fresh DNS lookup.
When you make large variably sized requests (for example, more than 128 MB), we advise tracking the throughput being achieved and retrying the slowest 5 percent of the requests. When you make smaller requests (for example, less than 512 KB), where median latencies are often in the tens of milliseconds range, a good guideline is to retry a GET or PUT operation after 2 seconds. If additional retries are needed, the best practice is to back off. For example, we recommend issuing one retry after 2 seconds and a second retry after an additional 4 seconds.
If your application makes fixed-size requests to Amazon S3, you should expect more consistent response times for each of these requests. In this case, a simple strategy is to identify the slowest 1 percent of requests and to retry them. Even a single retry is frequently effective at reducing latency.
If you are using AWS Key Management Service (AWS KMS) for server-side encryption, see Quotas in the AWS Key Management Service Developer Guide for information about the request rates that are supported for your use case.
