“This paper argues that the data warehouse architecture as we know it today will wither in the coming years and be replaced by a new architectural pattern, the Lakehouse, which will (i) be based on open direct-access data formats, such as Apache Parquet, (ii) have first-class support for machine learning and data science, and (iii) offer state-of-the-art performance.”Michael Armbrust, Ali Ghodsi, Reynold Xin, Matei Zaharia · Lakehouse: A New Generation of Open Platforms that Unify Data Warehousing and Advanced Analytics · 2021 · Lakehouse: A New Generation of Open Platforms that Unify Data Warehousing and Advanced Analytics, CIDR 2021 — rezumat
Bronze is the evidence, silver is the cleaned truth, gold is the answer.
The data lake promised cheap storage for anything: Parquet files on object storage, no enforced schema, no transactions. It often delivered a swamp: nobody knows what is clean, two jobs write over the same directory, a read catches half of a write. The classic warehouse has transactions, schema and speed, but in a closed format, as a copy of the data. The lakehouse puts an open table format between them (Delta, Iceberg, Hudi): a metadata log over the Parquet files that brings ACID transactions, "time travel" to an earlier version, schema evolution and, above all, several engines — SQL, Spark, an ML framework — reading the same files without copies. The medallion architecture organises the layers: bronze (data exactly as it arrived, never modified), silver (cleaned, deduplicated, correctly typed), gold (aggregated, modelled for consumption — usually as a star). The golden rule is that bronze is the evidence: anything in silver and gold must be rebuildable from it.
Why it matters When a transformation turns out to be wrong six months later, the only question that matters is whether you still have the raw data. Bronze answers yes.