A load testing developer designs and executes tests to evaluate the performance and behavior of software applications under various load conditions. They simulate multiple users or transactions to check if the application can handle the expected number of users or transactions in real-life scenarios. They identify bottlenecks, performance issues, and system limitations. They also analyze test results, make necessary changes, and retest to ensure the software's optimal performance. Additionally, they collaborate with other developers and stakeholders to establish performance criteria and standards, constantly working to improve the reliability and efficiency of the system.