Use a stream interface in the following circumstances: You are processing continuous data streams. Real-time or low-latency requirements apply. Input length is variable. Sample-by-sample processing fits the algorithm. You are building a pipelined dataflow. Use a buffer / window interface in the following circumstances: You are operating on fixed-size blocks. You are doing batch processing. The algorithm requires the complete dataset. Random access to data is required. Deterministic processing boundaries matter.