Final answer:
The AWS Step Functions service is primarily written in Node.js and allows for the use of other programming languages such as Java, Python, and C++ for defining the logic of Step Functions.
Step-by-step explanation:
The AWS Step Functions service is primarily written in Node.js. While it is developed using Node.js, you can use a variety of programming languages to define the logic of your Step Functions. These languages include Java, Python, and C++. However, the service itself is implemented in Node.js.