Are sandbox refreshes randomized as far as the instance it refreshes to?

Current Scenario:

  1. I'm on a non-preview instance.
  2. I would need to refresh after January 8th, 2022, the preview cutoff date. ​This will leave me on the non-preview.
  3. Then, the Winter release is completed.
  4. For the next Spring preview, assuming I haven't refreshed, am I already on a non-preview instance? Or it it random?

We want to be able to refresh our sandboxes on a regular cadence that aligns with the releases, but we want to maintain one of our full/partial sandboxes as a preview instance and one as a non-preview instance. Is there a way to predict that for the rest of the releases for the year? Our environment is heavily integrated with other systems, so refreshes can impact other systems, and we want to be able to coordinate this better.

2 Answers 2


The selected instances are not random as far as I can tell, but they are not publicly deterministic, either. Salesforce.com doesn't leave much to random chance, so it is likely heuristics that is based on several factors, including available space, population density, etc. It makes sense to move as many orgs as possible from heavily-loaded servers to lightly-loaded servers to rebalance hardware usage. The exact details are not disclosed to the public, as far as I can tell. As such, it is highly unlikely that even salesforce.com knows which instances will be upgrade instances more than a few weeks out, much less which instances would be selected in a future release cycle.

In other words, you cannot plan or determine if you are on a Preview Instance ahead of time, certainly not for the duration you're looking for. I won't presume what your use case is for these orgs, but you may want to investigate moving some of those uses to Scratch Orgs instead. Scratch Orgs can be configured to be either prerelease or not on demand, and you can use modern tools to import large amounts of data and metadata into those orgs on demand. Sure, it won't help with some types of tasks, but you might be able to offload some types of UAT/QA/regression tasks to orgs where you have more control (within the given time windows) over which release the org is created as.


Salesforce provided a simple way to determine this: https://sandbox-preview.herokuapp.com/cheatsheet

Basically, after the last release is released to production, any refreshes completed from the last release to the sandbox preview instance cutoff date will result in a preview instance. To avoid a preview instance, you would need to wait to refresh til after the preview cutoff and before the next release goes to production.

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