# Replacement caches ## Introduction Having [chosen to configure cache replacements for a virtual environment](https://doc.wearepatchworks.com/product-documentation/virtual-environments/implementing-virtual-environments/configuring-a-virtual-environment-version/configuring-virtual-environment-replacements/..#configuring-replacements-for-a-virtual-environment-version), a new replacement rule is displayed, ready for you to configure:

Having defined the first rule, you can add more - you must create one replacement rule for every cache that you need to replace in every process flow that will run in this environment. ## Need to know Please consider the [cache type](https://doc.wearepatchworks.com/product-documentation/process-flows/building-process-flows/process-flow-shapes/advanced-shapes/cache/add-to-cache-shape) used when replacing caches in [master process flows](https://doc.wearepatchworks.com/product-documentation/virtual-environments/implementing-virtual-environments/creating-a-master-process-flow).

Cache type Can be replaced in VE config? Can be used in master process flows? Cache key notes

Cache type	Can be replaced in VE config?	Can be used in master process flows?	Cache key notes
Company	Yes	Yes	We recommend that you always replace `company` caches in virtual environments, unless you have a good reason for not doing so. This ensures that caches are unique for each environment. Keep in mind that cache keys are NOT replaced. Provided that you replace the `company` cache in each virtual environment, this is not an issue - the cache in each environment will be unique. If, for some reason, you do not take this approach, please ensure that the given cache key in your master process flow utilises variables to ensure that it's unique at runtime - otherwise, cached data from one environment may overwrite data from another.
Flow	Yes	Yes	We recommend that you always replace `flow` caches in virtual environments, unless you have a good reason for not doing so. This ensures that caches are unique for each environment. Keep in mind that cache keys are NOT replaced. Provided that you replace the `flow` cache in each virtual environment, this is not an issue - the cache in each environment will be unique. If, for some reason, you do not take this approach, please ensure that the given cache key in your master process flow utilises variables to ensure that it's unique at runtime - otherwise, cached data from one environment may overwrite data from another. Please see Referencing variables for unique cache keys for more information.
Flow run	No	Yes	Behind the scenes, each cache key for a `flow run` cache is appended with a unique `flow run id` - although you never see this in the dashboard, it does mean that these caches will never clash between virtual environments. However, if required, you can reference an environment variable in the cache key name, so the cache key is immediately identifiable for each virtual environment. please see Referencing variables for unique cache keys for more information.

Company

Yes

We recommend that you always replace company caches in virtual environments, unless you have a good reason for not doing so. This ensures that caches are unique for each environment.

Keep in mind that cache keys are NOT replaced. Provided that you replace the company cache in each virtual environment, this is not an issue - the cache in each environment will be unique.

If, for some reason, you do not take this approach, please ensure that the given cache key in your master process flow utilises variables to ensure that it's unique at runtime - otherwise, cached data from one environment may overwrite data from another.

Flow

Yes

We recommend that you always replace flow caches in virtual environments, unless you have a good reason for not doing so. This ensures that caches are unique for each environment.

Keep in mind that cache keys are NOT replaced. Provided that you replace the flow cache in each virtual environment, this is not an issue - the cache in each environment will be unique.

Flow run No Yes Behind the scenes, each cache key for a flow run cache is appended with a unique flow run id - although you never see this in the dashboard, it does mean that these caches will never clash between virtual environments.

However, if required, you can reference an environment variable in the cache key name, so the cache key is immediately identifiable for each virtual environment. please see Referencing variables for unique cache keys for more information.

{% hint style="info" %} For more information on the different cache types, please refer to our [Add to cache](https://doc.wearepatchworks.com/product-documentation/process-flows/building-process-flows/process-flow-shapes/advanced-shapes/cache/add-to-cache-shape) documentation. {% endhint %} ## Defining replacement rules for a cache {% stepper %} {% step %} **Select the required ORIGINAL cache** Use the `original` dropdown list to select the first company cache in a 'master' process flow that must be replaced when this process flow runs in the given virtual environment - for example:

{% hint style="info" %} As you work through your replacement configuration, it's helpful to view related ['master' process flows](https://doc.wearepatchworks.com/product-documentation/virtual-environments/implementing-virtual-environments/creating-a-master-process-flow) in another browser tab. You can duplicate a Patchworks browser tab and navigate to a different page whenever needed. {% endhint %} {% endstep %} {% step %} **Select the required REPLACEMENT cache** Use the `replacement` dropdown list to select the replacement cache that must be used when this process flow runs in the given virtual environment - for example:

{% endstep %} {% step %} **Confirm your selections** Click the `create` button (associated with this replacement rule) to confirm your selections:

The rule is added:

{% hint style="info" %} Once a rule is confirmed, it can't be edited. If you need to change a replacement rule, use the 'trash' icon to remove it and add a new one. {% endhint %} {% endstep %} {% step %} **Add more replacement rules for caches** To add another replacement rule for a cache, click the top-right `create` button:

Update the new rule as required, then click the associated `create` button to confirm your selections:

Repeat as many times as needed to define all required cache replacements for all process flows that will be running in this virtual environment. {% hint style="info" %} If you don't want to define ALL cache replacements now, that's OK. For example, you might choose to add the minimum number of replacements needed for [testing](https://doc.wearepatchworks.com/product-documentation/virtual-environments/implementing-virtual-environments/testing-a-process-flow-against-a-virtual-environment), then define remaining rules (in a [new draft](https://doc.wearepatchworks.com/product-documentation/virtual-environments/implementing-virtual-environments/configuring-a-virtual-environment-version/understanding-virtual-environment-versions)) later, after initial testing is complete. {% endhint %} {% endstep %} {% endstepper %}