---
title: "Application update strategies"
description: "Control update parallelism, task order, monitoring, and failure actions."
---

> Documentation Index
> Fetch the complete documentation index at: https://cdelivery.dev/llms.txt
> Use this file to discover all available pages before exploring further.

# Application update strategies

The update strategy controls how replacement tasks are introduced. Operators and Admins configure it for each application.

## Settings and defaults

| Setting | Default | Effect |
| --- | --- | --- |
| Parallelism | All replicas | Number replaced together |
| Order | StopFirst | Stop the old task before starting its replacement |
| Monitor | 60 seconds | Observe replacement failures |
| Failure ratio | 0 | Tolerated failure proportion |
| Failure action | Rollback | Response when the failure threshold is crossed |

All-at-once, stop-first updates can interrupt every replica. Start-first needs spare resources and application support for overlapping instances. It does not automatically make a single-replica database safe to run twice against its data.

## Choose and verify

Review replica count, per-server caps, reservations, startup time, and whether multiple versions can operate concurrently. Select a smaller batch or start-first when the workload and available capacity support it.

Submit one change and observe task progression, errors, logs, and a real request. A task remaining alive through the monitor window is not equivalent to a business readiness assertion.

## Failure handling

A configured rollback restores the previous application configuration when available. Its own execution uses all-parallel replacement and continues on rollback failures; inspect the resulting state rather than assuming recovery completed.

Use [XHealth](/docs/guides/release-safety/xhealth/) for explicit assertions and [Guardian](/docs/guides/release-safety/guardian/) for candidate validation before promotion. See [rollback and failures](/docs/guides/release-safety/rollback/) for data and recovery boundaries.

Source: https://cdelivery.dev/docs/guides/release-safety/update-strategy/index.mdx