Glossary terms - E

Terms beginning with E cover the places code runs and how it is reached — environments, ephemeral preview environments, the edge and egress traffic. Every definition is short and citable.

3 terms

Environments
Environment parity
Environment parity is the practice of keeping development, staging and production environments as similar as possible: same operating system, same runtime version, same dependencies, same backing service types and data shape, so a change verified in one environment behaves the same way in the next. It is one of the twelve-factor principles.
Delivery pipelines
Environment promotion
Environment promotion moves a single built artifact through a chain of runtime environments - typically dev, staging and production - running the same tests and health checks at each stop. The artifact is not rebuilt between environments; only its target changes, so what you tested is exactly what ships.
Delivery metrics
Error budget
An error budget is the amount of unreliability a service is allowed over a fixed window: the gap between its target reliability (SLO) and 100%. Teams spend that budget on new releases and risky changes; when it runs out, they pause launches and prioritize stability until the window refills.