Great question — here’s how Prefect behaves in this situation. I’m assuming Prefect 3.x and a self-hosted server (behavior is the same as Cloud). What happens when you redeploy - If you redeploy with the same deployment name: Prefect performs an upsert. The existing deployment is updated in place; it does not create a new one. - Running flow runs: unaffected. Anything already Running will keep running with the configuration/version it was created with. - Future scheduled runs: all existing runs in Scheduled state for that deployment are cleared, then recreated according to the new schedules/config. - If you change the deployment name: Prefect will create a new deployment. The old deployment will keep scheduling until you pause or delete it — which can cause duplicate runs if both are active. Key implications - Safe to redeploy while runs are executing: you will not interrupt currently running flow runs. - You will lose the existing future Scheduled runs for an updated deployment (they’ll be replaced by new ones from the updated schedule). If you have near-term runs you must preserve, consider pausing scheduling first, then redeploying, then resuming. - Workers don’t need to be restarted, but if you changed the work pool name or job variables in your prefect.yaml, make sure your workers are pointing at the correct pool and that your job variables still align. Recommended workflow to avoid surprises 1) Keep the same deployment names if you just want to update them in place (this avoids duplicate deployments). 2) If you must rename a deployment, pause or delete the old one first to prevent duplicate scheduling. 3) If timing is critical, pause scheduling before redeploy and resume after: - List schedules:

prefect deployment schedule ls 'flow-name/deployment-name'

- Pause a schedule:

prefect deployment schedule pause 'flow-name/deployment-name' <SCHEDULE_ID>

- Resume a schedule:

prefect deployment schedule resume 'flow-name/deployment-name' <SCHEDULE_ID>

4) Redeploy from your project (reads updated prefect.yaml):

prefect deploy

Or target a specific flow entrypoint/name if you prefer:

prefect deploy ./path/to/file.py:flow_func --name 'flow-name/deployment-name'

5) Clean up old deployments when renaming:

prefect deployment delete 'flow-name/old-deployment-name'

Authoritative references - Deployment upsert behavior (scheduled runs cleared on update): Create deployment API - Deployment versioning behavior and what changes get versioned: Deployment versioning - Schedules concepts and management: Schedules and Create schedules - prefect.yaml usage: Using prefect.yaml A couple of clarifying questions so I can tailor the exact steps: - Are you keeping the same deployment names, or renaming them? - Do you need to preserve any of the already-created future Scheduled runs? - Did your prefect.yaml change the work pool name or just parameters/job variables/schedules?

Short answer: not exactly.

--name

supports glob-style patterns, but

all

is not a special keyword. -

prefect deploy -n all

will only select deployments literally named

all

. It won’t match A, B, C unless one of them is named

all

. - To upsert all deployments defined in your current project’s prefect.yaml, either: - Run without a name filter:

prefect deploy

(add

--no-prompt

if you want it non-interactive), or - Use a glob that matches everything:

prefect deploy -n '*'

And yes, when the same qualified deployment names are selected (e.g., your existing A, B, C), Prefect will upsert them in place: - Running flow runs are unaffected. - Future Scheduled runs for those deployments are cleared and recreated from the updated schedule/config. Docs for reference: - Deploying from a project/prefect.yaml: Create deployments - prefect.yaml usage: prefect.yaml - Upsert behavior (API): Create deployment API

Thanks for clarifying. -

prefect deploy --all

will deploy all deployments defined in your current project (from your prefect.yaml). If those deployments already exist (A, B, C), Prefect will upsert them in place. -

prefect deploy -n all

is different — it filters by name/pattern. It will only target a deployment literally named

all

(unless you actually have one). It will not match A, B, C. Reminder of effects when upserting: - Running flow runs: unaffected. - Future Scheduled runs: cleared and recreated from the updated schedules/config. Examples: - Upsert all deployments from prefect.yaml:

prefect deploy --all

- Or using a glob to match everything:

prefect deploy -n '*'

Docs: - Deploying from a project: Create deployments - Upsert behavior (API): Create deployment API