Data Lake

A data lake is cheap, large-scale storage that holds raw data in almost any format — tables, JSON, text, images, video, log files — without forcing it into a fixed structure first. You dump data in as-is and decide how to make sense of it later, which is called “schema on read” (you impose the structure when you query, not when you store).

Lakes are popular because storage is cheap and you keep everything, including data you are not sure you need yet. The danger is the “data swamp”: with no governance, naming, or documentation, a lake fills with files nobody can find or trust. That risk is what pushed the industry toward the lakehouse, which adds warehouse-style structure on top of lake-style storage.