Strata: A Semantic Layer That Refuses Invalid Queries Before Your LLM Runs Them

Strata is a full-stack analytics platform built around a governed semantic layer — one that validates queries and returns a refusal instead of a wrong number when a request doesn't fit the model. It's built by Ajo, who spent four years at Netflix working on self-service analytics for non-technical business users.

The core design bet is strict naming. Only one thing called Revenue can exist in a project. If revenue maps to multiple tables, query grain plus speed decides which table gets used. That constraint is what makes the rest of the system work.

Cross-domain blending without double counting

Because facts share conformed keys (e.g. a conformed Date key), Strata can join two fact domains — Orders and Support — into one blended result. Each fact is aggregated to the common grain and joined on conformed keys, never fact to fact. The team claims the system cannot double count, and agents get an explicit refusal rather than a wrong number.

Partition and aggregate-aware routing

Strata routes each query to the fastest engine that can answer it, falling back to the warehouse when filters fall outside the hot tier:

• Hot tier: ClickHouse or Druid
• Warm tier: Snowflake
• Cold tier: AWS Athena

You can load a portion of your data into a fast engine while keeping full history in Trino or something cheaper. The router picks the faster tier when the query can be resolved there.

Measure types and cohorts

Five measure types ship out of the box: Standard, Complex, Snapshot, Exclusion LOD, and Inclusion LOD. On top of that, users can build custom calculations that span fact domains, and segments that restrict a view or a single measure to a cohort — e.g. new customer revenue beside total revenue in one view.

Model as code

The whole model is two YAML file types plus the naming convention. The workflow: your coding agent drafts the YAML, strata audit validates it against the warehouse, and Git carries it to production. No view/explore/cube to pick first — every step is validated and previewed as you build.

Who it's for and how to try it

Strata is explicitly not a semantic layer your existing BI tool connects to — the team calls that a dead end. Instead it ships its own dashboards, subscriptions, scheduled reports, a Google Sheets add-on, row-level security, plus an API and MCP server for anything you build on top. It's in early beta, not open source, but the free tier covers up to 25 users and runs entirely on your machine via Docker.