Issue sorting Clients by latest Appointment when using Big Tables

I’m having an issue sorting a collection when the data source is a Glide Table that relies on computed columns linked to a Big Table.

Context
• I’m building a CRM to manage Clients and Appointments
• Main tables:
Clients
Appointments (Big Table, expected 50k+ rows)
• Users need to quickly see how long it has been since the last completed appointment with each client
• Appointments can be:
• completed
• not completed
• planned in the future (it’s just a future appointment with completed not true)

Current setup
• A Glide Table (Clients → Big Table) linked to the Appointments Big Table
• In the Clients table I created:
• a Lookup column that retrieves only completed appointments for each client
• a Single Value column that extracts the most recent completed appointment
• Data retrieval works as expected

Problem
• I can’t sort a collection based on the latest appointment date coming from these computed columns
• I tried multiple approaches (lookup, single value, different source columns), but sorting doesn’t work when the data originates from a Big Table

Goal
• calculate how many days have passed since the last completed appointment
• assign a frequency/status label (e.g. recent / overdue)
• sort clients by their most recent appointment

Is this a known limitation when working with Big Tables, or is there a recommended data modeling pattern or workaround to achieve this?

Thanks in advance for any suggestions or best practices.

Big Tables cannot sort on calculated fields, so the workaround is to use a workflow to assign a calculated value to a basic column which can then be used as a sort field.

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