Data Science Summit 2025: Super-fast Access to Unstructured JSON: the ClickHouse® Way

CONFERENCE TALK

Data Science Summit 2025: Super-fast Access to Unstructured JSON: the ClickHouse® Way

Maciej Bak, Support Engineer at Altinity, speaks at the Data Science Summit 2025. The origins of the Data Science Summit date back to 2014, when the first Data Science Warsaw community meeting was held. It was the popularity of these periodic meetups that contributed to the decision to organize the first edition of the conference, and its success led to subsequent editions. Currently, DSS is the largest Polish community focused on the *data* field.

Maciej’s talk – Super-fast Access to Unstructured JSON: the ClickHouse® Way is about indexing JSON, which has always been a challenge. Even databases built around documents, like MongoDB, struggle to make unstructured data both flexible and fast. Until now, ClickHouse users had to lean on pipelines, materialized views, or Map hacks to query JSON at scale.

With the new native JSON data type, things get much simpler and robust. We’ll show how ClickHouse can filter unstructured JSON with an index on every field—at minimal cost and without complicated pipelines. Along the way, we’ll cover:

• How the new JSON type works under the hood.
• Where its current limitations lie.
• How to add an index for lightning-fast lookups.
• What our tests revealed—strengths, trade-offs, and surprises.
• What’s next from ClickHouse developers to push this even further?

Perfect for:
Data engineers, SREs, and analytics teams who wrangle unstructured logs, events, or telemetry and want speed without extra ETL.

Key takeaways:
You’ll see how querying JSON directly in ClickHouse removes entire layers of pipeline complexity. You’ll learn where it shines, where it still has rough edges, and how indexing tricks make messy data feel fast. You’ll leave with a clear view of what’s possible today—and what’s coming next.

About the Presenter

Maciej Bak – Support Engineer at Altinity

Maciej is a passionate and self-driven engineer with a long-standing interest in programming and data. His journey began in primary school with Basic, evolving into high-level object-oriented languages like Delphi and Java.
In high school, he discovered his passion for databases while building websites in HTML, PHP, JS, and CSS. Since then, he explored the full spectrum of database technologies—from SQLite and MySQL to Firebird, Oracle, PostgreSQL, and now ClickHouse.
Today, he specialized in distributed systems, big data analytics, and cloud-native architectures, working with tools like Kubernetes, Kafka, and Apache Iceberg.
He is curious, empathetic, and always learning—committed to continuous growth and helping others solve complex technical challenges with clarity and precision.