Improper design choices in AWS Step Functions can lead to unnecessary charges. For example: * Using **Standard Workflows** for short-lived, high-frequency executions leads to excessive per-transition charges. * Using **Express Workflows** for long-running processes (close to or exceeding the 5-minute limit) may cause timeouts or retries. * Inefficient use of states—such as chaining many simple states instead of combining logic into a Lambda function—can increase cost in both workflow types. * Overuse of payload-passing between states (especially in Express workflows) increases GB-second and data transfer charges.