Based on your knowledge of current ECS models will your workflow cross tenant boundaries? If yes the following checklist may help you determine what features you need to create to enable your funcitonality for libraries using ECS.

General

Build a workflow for your feature for non-ecs FOLIO that identifies the objects (Eg. User, order line, request, item etc.) needed at each stage of the workflow
Identify where the objects (Eg. User, order line, request, item etc.) in your workflow are created/edit. Are they created by the member library or Central office?
For each object highlight the "Links" or "References" that object has to other objects
For each stage of the workflow. Identify the linked objects that are not available in the tenant in which the primary object is stored.
Consider how the user might manage this linked object with the current design by adding a tenant selection to the search or filter component.
Create a Jira feature for this functionality and label it "ecs"

Design

Consider how a user might accomplish the task within a single-tenant environment. Does that experience actually need to change when considering additional tenants? Where does it fall short and why?
Could tenant context be pre-determined by the current affiliation for all the actions the user is taking?
Could the user simply specify a specific tenant context with a dropdown in order to accomplish the task?

Permissions

Consider whether the object should be editable with permissions from the specific data tenant OR permissions from central tenant. Are there use cases that support allowing permissions to be controlled a certain way?
What access/permission flexibility is required? Should all users be able to see linked data or only users with permissions in the tenant where the data is being stored?

Performance

This should be similar to considering performance for regular FOLIO.
Think about how much of it will be done
How frequently
How many concurrent users.
This will certainly be more complicated to test and optimize so leave extra time whenever possible particularly as teams are learning ECS.

Scalability

In designing features you must consider first how they will work within a tenant. Scaling up to multi tenant should NOT require significant changes to the user experience.
What minimal UI changes could you propose for ECS enabled system that would allow users to complete the workflow?

Testing

Create stories to test what should or should not appear when ECS IS NOT enabled.
Create stories to test what should or should not appear when ECS IS enabled.
Is the behavior different when the user is in the data tenant vs central tenant?
Test permissions in both central and data tenant(s).

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