Sandboxes That Cost Nothing

If you work with external APIs, you know the problem. There is no dev.github.com , no staging.api.companieshouse.gov.uk , no test endpoint for the thing you actually depend on. Production is the only source. So how do you get a development environment without re-fetching everything you already have? The usual answer is to copy: duplicate the warehouse, or keep a separate dev database and sync it periodically. Both are slow, both drift, and both cost storage in proportion to the number of people on the team. Interlace does something else. An environment is not a copy of your data, it is a set of views over it. Fingerprints first Every model gets a fingerprint: a hash of its canonical SQL — or its Python source — together with its strategy configuration and its upstream fingerprints. A build writes an immutable physical table named after that fingerprint. interlace__main.orders__a1b2c3 That table never changes. If the model's definition changes, the new version gets a new fingerprint and a new table, and the old one stays exactly where it is. An environment is then just a set of views pointing at fingerprinted tables. Production is the unprefixed namespace; every other environment prefixes its schema. Environment View for main.orders prod main.orders dev dev__main.orders pr-142 pr-142__main.orders Consumers and BI tools connect to main.orders and never learn that a fingerprint exists. There is no environment list to configure, either — an environment exists once something has been promoted to it. Why the sandbox is free Here is where the re-fetching problem disappears. Applying to a sandbox does not rebuild models whose fingerprint already exists. It points the sandbox's views at the tables production already built. interlace apply --env dev Change one model out of forty and the sandbox builds one model. The other thirty-nine are reused — not copied, reused, the same physical tables production is reading. The expensive source extract that ran this morning is the table