What is Data Lake? — UK Software Development Guide

4 min readJune 2025ClickMasters Technical TeamReviewed by James Whitmore, CTO
what is a data lake

Direct Answer

A data lake is a centralised repository that stores large volumes of raw data in its native format until needed — structured data (database tables), semi-structured (JSON, CSV logs), and unstructured (images, documents, audio). Unlike a data warehouse (which stores pre-processed, structured data), a data lake stores raw data and transforms it only when queried.

Data-lake in the UK

Data lakes have specific UK GDPR compliance challenges. Raw data in a data lake may include personal data that was collected for one purpose but retained indefinitely "for future analytics" — violating the data minimisation principle (UK GDPR Article 5(1)(c)). UK GDPR right to erasure (Article 17) is technically complex for data lakes: raw data files may contain personal data mixed with non-personal data, making deletion without data loss difficult. ClickMasters recommends: zone architecture (raw → cleansed → curated), UK GDPR retention policies enforced at the raw zone (automated deletion after defined period), and pseudonymisation before data reaches the curated zone.

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