What is a Two-Way Sync?

One-way sync only pushes updates from a source system to a destination, so editing the destination directly gets silently overwritten or ignored on the next sync. Two-way sync instead detects a change on either side, such as a field edited in a CRM or in a connected calendar, and writes that change back to the other system, typically using timestamps, version numbers, or change logs to determine which update is newer when both sides changed the same record close together. The hard part of two-way sync is conflict resolution: if a record is edited in both systems before the next sync cycle runs, the platform needs a deterministic rule, such as last-write-wins or field-level merging, to avoid silently discarding one of the changes or, worse, looping the same update back and forth forever. Well-implemented two-way sync also needs idempotent writes so a retried sync doesn't duplicate data.