Announcement: Updated default retry behavior (2026)

[millems]

This issue tracks the 2026 retry updates for AWS SDK for C++. See the announcement blog post for the full story across all AWS SDKs, including how to tell if you are affected.

Status

Opt-in	Coming in the following weeks. We will update this issue when the release ships.
Opt-in flag	AWS_NEW_RETRIES_2026=true
Default rollout	No sooner than November 2026

What changed

When you set AWS_NEW_RETRIES_2026=true, the default retry mode changes from legacy to standard. Several other retry defaults also update. The standard mode adds a retry quota that limits retries when failures are widespread, so your application fails fast instead of waiting on retries that are unlikely to succeed. This also helps outages resolve faster.

If you have explicitly configured a retry mode, max attempts, or backoff, your value takes precedence for that setting.

Setting	Before	After
Default retry mode	legacy	standard
Transient (non-throttling) base delay	25 ms	50 ms
Throttling base delay	25 ms	1,000 ms
Max attempts	11	3
Retry quota	None	500 tokens
Transient retry quota cost	5 tokens	14 tokens
DynamoDB and DynamoDB Streams
Transient (non-throttling) base delay	25 ms	25 ms (unchanged)
Throttling base delay	25 ms	1,000 ms
Max attempts	11	4

DynamoDB defaults use a shorter base delay to match its low-latency profile. The additional attempt keeps the last retry's maximum backoff comparable to the general default.

Transient errors (such as 500s and connection resets) now use a much shorter backoff than throttling errors (where the service asks you to slow down). For details on backoff timing, error classification, and the retry quota, see Retry behavior in the AWS SDKs. For retry mode selection and configuration options, see Retry behavior in the AWS SDKs.

How to opt in

Once the release ships (we will update this issue), set the environment variable:

export AWS_NEW_RETRIES_2026=true

How to revert

During the opt-in period, remove the environment variable:

unset AWS_NEW_RETRIES_2026

After the default rollout (no sooner than November 2026), the new behavior becomes the default. To restore previous behavior, set the retry mode to legacy:

export AWS_RETRY_MODE=legacy

Or in the shared config file (~/.aws/config):

[default]
retry_mode = legacy

Where you might notice a difference

For most workloads, the change is invisible or strictly better. Transient errors recover faster because the base delay is significantly shorter.

• Max attempts decreased. If your workload relied on a higher retry count to eventually succeed, you may see more errors surfaced to your code. You can override max_attempts to restore your previous value.

• This SDK now has a retry quota. Legacy mode had no standardized retry quota. The SDK would retry up to the max attempt count regardless of how many requests were failing. Standard mode tracks a token budget and returns errors directly when failures are widespread, so your application fails fast and frees up resources for requests that can succeed. For details, see retry quota.

• Retry quota activates sooner for transient errors. Each transient retry costs 14 tokens (previously 5 for most errors). During sustained transient failures (such as 500s and connection resets), the retry quota triggers at a lower failure rate than the previous version of standard mode. Throttling retries cost 5 tokens.

• Long-polling operations now back off when the retry quota is depleted. Operations like SQS.ReceiveMessage apply a backoff delay before returning an error, even when retries are blocked. Without this, polling loops tighten during outages, spiking client CPU usage and generating additional load that can delay recovery. For details, see long-polling operations.

Overriding specific settings

You do not have to accept all changes as a bundle. If you opt in but want to keep a specific previous value, set it explicitly. Precedence applies per setting.

For example, to use the new backoff timing but keep a higher DynamoDB max attempts:

#include <aws/core/Aws.h>
#include <aws/core/client/ClientConfiguration.h>
#include <aws/core/client/DefaultRetryStrategy.h>
#include <aws/dynamodb/DynamoDBClient.h>

Aws::Client::ClientConfiguration clientConfig;
clientConfig.retryStrategy = Aws::MakeShared<Aws::Client::DefaultRetryStrategy>(
    "Alloc", 10 /* maxRetries */);
Aws::DynamoDB::DynamoDBClient client(clientConfig);

For the full list of configurable settings and their precedence, see Retry behavior in the AWS SDKs.

Feedback

If you encounter unexpected behavior or have questions, comment on this issue. Your feedback during the opt-in period directly shapes when and how we make this the default.