Exact Online–Trello integration without sync loops (implementation guide)
If you’re trying to keep Exact Online orders and Trello cards in sync in both directions, the biggest risk isn’t “can I connect them?”—it’s building a setup that doesn’t create duplicate records, overwrite newer changes, or loop endlessly.
Photo by Tim Mossholder on Unsplash
This guide walks through a practical way to design a bidirectional sync using an automation layer (like Zapier or Make), including field mapping, loop prevention, conflict rules, and a phased rollout plan.
What you’re actually trying to automate
Most teams want something like this:
When a new order is created (or received) in Exact Online, create a corresponding Trello card.
As the order moves through departments, updates in either system (Exact Online or Trello) should reflect in the other.
The team stops doing “triple entry” (email + Trello + Exact Online) and can trust one workflow.
Step 1: Define the “source of truth” per field (don’t sync everything)
A bidirectional sync only works when you decide which system owns which fields.
Create a simple mapping table (even in a spreadsheet) and label each field as:
Exact-owned (Trello can display it, but shouldn’t write it)
Trello-owned (Exact can display it, but shouldn’t write it)
Shared (both can write it, but then you must have conflict rules)
Common safe defaults:
Exact-owned: order number, invoice/financial fields, customer record references
To update records safely, each side needs a reliable “pointer” to the other.
Recommended pattern:
Store the Exact Online Order ID on the Trello card (e.g., in a custom field).
Store the Trello Card ID on the Exact Online record (if you have a place for a custom field / note / reference).
If you can’t store both directions, store at least one direction and also store a dedupe key (e.g., Order Number) so your automation can search before creating.
Step 3: Prevent sync loops (the #1 problem in bidirectional automation)
A sync loop is when:
Exact updates → automation writes to Trello → Trello update triggers automation → writes back to Exact → repeat.
Use one (or more) of these loop-prevention strategies:
Strategy A: “Last updated by integration” filter
If your tools expose “last updated by” metadata, filter triggers so that changes made by the integration user don’t trigger the reverse scenario.
Strategy B: Add a “Sync source” / “Updated by” marker field
Create a field that your automation sets when it writes an update.
Examples:
Last sync source = Exact or Last sync source = Trello
Last updated by automation = true
Then, in your triggers, add a guard like:
“Only run if last sync source is not the opposite system”
Strategy C: Use timestamps + a minimum delay window
For shared fields, compare last_modified_at timestamps.
A simple rule that prevents thrash:
If both sides changed within (say) 60–120 seconds, treat as a conflict and don’t auto-overwrite.
Step 4: Define conflict rules (what happens if both sides change?)
Conflicts are inevitable once you allow bidirectional updates.
Pick one approach:
Option 1: Exact wins for shared fields
Safer when Exact is the operational system.
Option 2: Trello wins for workflow fields
Safer when Trello drives internal execution.
Option 3: “Newest wins” with logging
Works when your data is clean and you can trust timestamps.
Always log what changed (even if it’s just a comment on the Trello card).
Step 5: Choose your automation layer: Zapier vs Make (for this pairing)
Both can work for Exact Online ↔ Trello. The decision usually comes down to complexity.
Zapier: faster to build, simpler maintenance, great when your mapping rules and conditions are straightforward.
Make: better for complex branching, advanced transforms, and more “engineering-style” workflows.
If you’re already feeling the workflow is “overwhelming,” start with Zapier and only move to Make if you actually hit a ceiling.
Step 6: Roll out in phases (so you don’t break operations)
A practical rollout plan:
Phase 1: Skeleton one-way flow (Exact → Trello)
New orders create cards
Minimal field mapping
No bidirectional updates yet
Phase 2: Add safe updates (Exact → Trello)
Update a limited set of fields
Keep Trello-owned fields out of scope
Phase 3: Add bidirectional updates for 1–2 shared fields
A small fabric manufacturer lost inventory to handwritten label corrections. Connex fixed their Zapier stack, migrated ownership, and automated notifications — saving ~$17k/yr.
A practical Airtable to Supabase sync plan for new rows, updates, and backfill, using stable record IDs, unique constraints, and UPSERT to prevent duplicates.