Delta Lake

Delta Lake is an open-source storage framework that layers ACID transactions, schema enforcement, and time-travel on top of Apache Parquet files in cloud storage (S3, ADLS, GCS). Every table change is recorded in a transaction log, enabling point-in-time queries, schema validation, and multi-writer safety. Unlike traditional data lakes (which can accumulate duplicates, schema mismatches, and corrupted partitions), Delta ensures every read sees a consistent snapshot. It's not a database or warehouse—it's a storage layer. You query Delta tables using Spark SQL, Databricks SQL, or any engine that understands the Delta protocol. This makes it cheaper than Snowflake (pay-as-you-go compute) while maintaining data integrity guarantees.