Abstract: Methods, systems, and computer program products are described herein for implementing a workflow development system that enables users to incorporate custom functionality within a workflow. During runtime execution of the workflow, the custom functionality (e.g., custom code) is executed in a sandboxed environment, thereby ensuring that the custom code consumes only a limited amount of computing resources (e.g., processing power, memory, storage, etc.) that may be shared with other processes. The foregoing may be achieved without requiring the user to be aware that a sandboxed environment is being utilized. Instead, the user simply needs to select and associate a custom function with a particular workflow step, and the workflow development system manages the interactions with the sandboxed environment without any further user involvement.