Better Writeback for Microsoft Fabric? Fabric Data Apps vs Power BI

I've been using Power BI Translytical Task Flows for writeback since day 1. They solve a long standing problem of Power BI reports being read-only. But the more complex the workflow gets, the more you start fighting the limitations of building transactional experiences inside Power BI.

Microsoft Fabric Data Apps, built on Rayfin, take a different approach: instead of adding writeback to a report, you build an actual web application with its backend hosted in Microsoft Fabric.

A practical FP&A example

For the video, I built a simple variance commentary app.

Users see P&L items, Actual, Budget and Variance. When a variance is material, they can enter a comment which is stored directly in a Fabric SQL Database.

This is a common FP&A workflow that is still often run through Excel files distributed between teams and later consolidated manually. With a Data App, the commentary is stored centrally and can be reused for reporting and historical analysis.

From idea to working app in 10 minutes

Additional benefit of using Fabric Data Apps is their accessibility for LLM agents.

I gave a coding agent a few high-level requirements:

• show P&L items and variances
• highlight material variances
• allow users to enter comments
• track who submitted them
• store everything in Fabric SQL Database

And around ten minutes later, I had a working application writing data into Fabric SQL.

Obviously, a production FP&A application would need much more time and attention.

When writeback outgrows the feature

A simple writeback scenario might start with just a comment box.

However quickly come additional requirements: forecast versions, security, approvals, notifications, filters, richer validation and more complex interactions. At some point, you're no longer adding a one-off action to a Power BI report. You're building an application inside one.

Fabric Data Apps let you build that application directly, with much more control over the UX and with standard web development tools that coding agents can work with very effectively.

Surprisingly: Power BI User Data Functions used by Translytical Task Flows can't currently be reused natively by Rayfin apps. The two remain separate. Strange omission by Microsoft.

Which one to use?

As always: it depends.

If it's simple interaction accompanying Power BI report - TTF might suffice.

But when the writeback workflow starts requiring its own UI, navigation, validation and business logic, Fabric Data Apps are the way to go.