Branch Strategies and Release Modes for Continuous Delivery

This excerpt from the book Continuous Delivery 2.0 discusses how enterprises should choose a branch strategy based on product type, release frequency, team capability, and infrastructure such as test automation and environment management.

Three Release Modes

There are three basic release modes: Project Release Mode, Release Train Mode, and Intercity Express Mode. All share three constraint variables—Schedule, Features, and Quality—so fixing any two leaves the third adjustable.

In Project Release Mode, the feature set and quality criteria are defined up front; the release occurs only after all features are completed and meet the quality standard. This model suits commercial packaged software but can suffer from long cycles and difficulty handling requirement changes.

Release Train Mode is common in large, multi‑product enterprises. Each product line follows a pre‑planned schedule (like a train) to align releases across dependencies. It typically uses quarterly windows, emphasizes strict timing, and requires coordinated planning among teams.

The Release Train planning process includes detailed data such as release identifiers, deployment dates, risk levels, lifecycle milestones, tasks per phase, and responsible owners.

Intercity Express Mode fixes schedule and quality while allowing very short cycles (days to weeks). Teams can choose which “express” to board without long‑term commitment. It is popular for SaaS and internet services, reducing coordination cost and giving clear release dates, but demands high code quality and strong quality‑gate infrastructure.

Examples include Facebook’s evolution from a twice‑daily “trunk‑development, branch‑release” model to a nine‑to‑ten‑times‑daily “trunk‑development, trunk‑release” cadence.

The article concludes that as release cycles become shorter, trunk‑based development becomes advantageous, and the Intercity Express mode is advocated as the preferred continuous‑delivery pattern.