Issue number: closes #8257

Summary

Changes

This PR adds a Circuit Breaker utility (under the circuit_breaker_alpha namespace) so a Lambda function can stop calling an unhealthy downstream and let it recover, instead of piling on retries.

It ships as alpha on purpose: I want about a month of feedback before we lock the public API and promote it to GA.

The failure counter lives in memory per execution environment, so a healthy circuit writes nothing; we only persist state transitions. State is shared via DynamoDB, fails open if the store is unreachable, and uses a conditional write to elect a single probe during recovery (no thundering herd). You handle rejected requests with an on_circuit_open callback and observe state changes with an on_transition hook.

User experience

Before, you had to build the state machine, shared storage, and recovery logic yourself. Now you wrap the function that makes the downstream call:

from aws_lambda_powertools.utilities.circuit_breaker_alpha import circuit_breaker
from aws_lambda_powertools.utilities.circuit_breaker_alpha.persistence import (
    CircuitBreakerDynamoDBPersistence,
)

persistence = CircuitBreakerDynamoDBPersistence(table_name="CircuitBreakerState")


@circuit_breaker(name="payment-backend", persistence_store=persistence)
def charge(order: dict) -> dict:
    return payment_api.charge(order)

With no config, sensible defaults apply (open after 5 failures, probe after 30s, close after 3 successes). When open, the call is skipped and the callback's value is returned, or a CircuitBreakerOpenError is raised.

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

Disclaimer: We value your time and bandwidth. As such, any pull requests created on non-triaged issues might not be successful.