What Is a Data Lake and What Is a Data Lakehouse?
Over the last decade, the world of data architecture has gone through several transformations. From traditional data warehouses to Hadoop-based data lakes and now to the emerging Lakehouse paradigm, each stage represents a response to new challenges in scale, cost, and flexibility.
But what exactly is a Data Lake, and how does a Data Lakehouse extend it?
The Data Warehouse (Before Lakes)
Before discussing lakes, it’s important to recall the role of the data warehouse:
- Structured data only.
- Optimized for analytics (OLAP).
- Expensive, rigid, and not designed for semi-structured or unstructured data.
Examples: Teradata, Oracle Exadata, Microsoft SQL Server Analysis Services.
By the late 2000s, the rise of web-scale data and unstructured formats exposed the limits of this model.
The Data Lake
A Data Lake emerged as a response to these limitations.
Definition
A Data Lake is a centralized repository that allows you to store all data, in any format, at scale, and at low cost.
Key Features
- Raw storage: Keep data in its native format (CSV, JSON, logs, images, video).
- Schema-on-read: Structure is applied when data is queried, not when it is stored.
- Cost efficiency: Built on commodity hardware or object storage (HDFS, S3, MinIO).
- Flexibility: Can hold structured, semi-structured, and unstructured data.
Weaknesses
- Without proper governance, a Data Lake can turn into a “data swamp.”
- No transactional guarantees for updates/deletes.
- Hard to provide consistent performance and reliability for BI users.
The Data Lakehouse
As organizations adopted Data Lakes, a new problem appeared: business users still needed the reliability and transactional consistency of a data warehouse. Analysts wanted SQL queries, ACID compliance, and governance—but without sacrificing the flexibility of lakes.
The result was the Lakehouse.
Definition
A Data Lakehouse combines the scalability and flexibility of a Data Lake with the transactional consistency and SQL capabilities of a Data Warehouse.
Key Features
- Table formats with ACID transactions: Iceberg, Delta Lake, Hudi.
- Unified storage: Structured and unstructured data coexist in the same repository.
- SQL-native queries: Engines like Trino, Spark SQL, and Athena query lakehouse tables directly.
- Governance & schema evolution: Catalogs (Hive Metastore, Glue, Nessie) provide consistency.
- Performance: Optimizations like columnar formats (Parquet/ORC) and caching.
Comparing Data Lakes vs. Lakehouses
| Feature | Data Lake | Data Lakehouse |
|---|---|---|
| Storage | HDFS, S3, GCS, MinIO | Same (object storage or HDFS) |
| Data formats | CSV, JSON, Parquet, ORC | Columnar formats + transactional tables (Iceberg, Delta, Hudi) |
| Schema | Schema-on-read | Schema-on-read + schema evolution |
| Transactions (ACID) | No | Yes (through table formats) |
| Query engines | Spark, Presto/Trino, Hive | Spark, Trino, Athena, Flink |
| Use cases | Raw storage, data science, ML prep | BI, dashboards, advanced analytics, ML |
Real-World Examples
- Data Lake: Storing raw web logs, clickstream events, IoT data in S3.
- Lakehouse: Running BI dashboards in Trino/Athena directly on Iceberg tables stored in S3.
In other words, the Lakehouse bridges the gap: you no longer need to ETL all your raw data into a traditional warehouse—you can analyze it where it lives, with reliability.
Conclusion
- A Data Lake is the raw, flexible, and cheap storage layer for all types of data.
- A Data Warehouse is structured, rigid, and optimized for BI but limited in scope.
- A Lakehouse merges the two: it adds transactional consistency, governance, and SQL capabilities on top of a Data Lake.
This hybrid approach has become the new standard for modern analytics, with technologies like Trino, Iceberg, Delta Lake, and Hudi leading the way.