Implement Multi-Region Active-Active Campaign Projections Using Conflict-Free Replicated Data Types

[Emmyt24]

Description

The backend's campaign projection currently assumes a single writer region; running active-active across two regions for availability requires conflict resolution for concurrent writes to the same campaign row from both regions, which last-write-wins cannot safely provide for accumulating fields like pledged amounts.

Requirements and Context

• Model the campaign projection's mutable fields as CRDTs (e.g. a PN-counter for pledged amount, an OR-set for participant list) that merge deterministically regardless of arrival order or origin region
• Implement a merge process that reconciles concurrent updates from two simulated regions into a single converged state, with a test proving convergence regardless of merge order
• Document which fields can be safely modeled as CRDTs and which genuinely require single-writer semantics, and how those are handled instead
• Proof of work (required): this is a hard/complex issue — the PR description must include (1) a screenshot of the full relevant test suite run showing all tests passing, and (2) a screenshot of a successful project/module build or compile (npm run build) with no errors. PRs missing either screenshot will not be reviewed.

Suggested Execution

Branch: feat/integration-crdt-campaign-projections

Implement Changes

• Implement PN-counter and OR-set CRDT types for the relevant campaign projection fields
• Add a merge function invoked when reconciling two regions' projection state, with conflict-free, order-independent merging
• Add a property test (using fast-check) asserting merge(A, B) == merge(B, A) and convergence under randomized concurrent update sequences
• Document the single-writer fields left out of CRDT modeling and why

Test and Commit

Run npx vitest run src/__tests__/crdtCampaignProjection.test.ts — property-based merge-order-independence and convergence tests both pass. Then run npm run build and confirm it completes with no errors. Attach a screenshot of both the passing test run and the successful build to the PR description as proof of work.

Example Commit Message

feat(integration): CRDT-based multi-region active-active campaign projections

Closes #<issue>

Guidelines

• Branch from main, open a PR back to main
• All new code must have corresponding tests
• Run npm run lint and npm run test before pushing
• Follow existing naming conventions and file structure
• PR description must reference this issue number (e.g., Closes #<issue>)
• Keep commits atomic and use conventional commit format
• This is a hard/complex issue: PR must include a screenshot of the test suite passing and a screenshot of a successful build/compile — PRs without both screenshots will be marked incomplete and not merged