What is Delta Lake

Definition

Delta Lake is an open-source storage layer that brings ACID transactions, scalable metadata, schema enforcement, and time-travel versioning to data lake files, turning ordinary Parquet storage into a reliable foundation for lakehouse architectures.

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Adds ACID transactions to lake files so concurrent reads and writes stay consistent
Enforces schema and tracks versions, preventing silent corruption of tables
Enables time travel to query or restore previous versions of a table
Optimises query performance on lake storage through data skipping and compaction

Real World Example

A retailer stores its sales tables as Delta Lake on cloud object storage, so a failed batch job can roll back atomically and analysts can query yesterday's version of a table for a point-in-time reconciliation.

FAQs

What does Delta Lake add to a data lake?

It adds ACID transactions, schema enforcement, versioning with time travel, and performance optimisations on top of open Parquet files.

What is the transaction log in Delta Lake?

An ordered record of every change to a table that enables atomic commits, consistency, and time-travel queries.

How does Delta Lake relate to the lakehouse?

It is one of the open table formats that make the lakehouse possible by giving lake storage warehouse-grade reliability.