Apache Beam on GCP: How Distributed Data Pipelines Actually Work (for REST API Engineers)

Apache Beam is a declarative programming model for large-scale data processing, not a service or framework like a REST API. Instead of handling individual requests, it defines how data flows through transformations, while runners like Google Cloud Dataflow decide how that logic executes at scale. Cloud Composer orchestrates when pipelines run, Terraform defines where they run, and Beam itself focuses purely on what should happen to the data—making pipelines scalable, replayable, and reliable by design.