ReferenceGlossary
Expand and contract
A way to change a schema without locking a table: add the new column or table, write both, backfill, switch the reads, then drop the old one. Every step is backward compatible, so old and new code run side by side.
Data
In Quorum#
Expand and contract research removes the Schema migration lock Incident entirely. With only Online schema migrations the Incident is about eight times less likely, and with Expand and contract it cannot happen. Both cost Dev Hours: on a relational Database, a Feature that adds a query shape costs 10% more with online migrations and 25% more with expand and contract.
Design#
Read next#
Blue-green deployment, Feature flag, Tech debt, Strangler pattern