Migrate existing referrals

An existing referral system usually contains two different kinds of data:

1. active advocate codes that may still be in circulation;
2. historical conversions whose rewards were already issued.

Treat them differently. The most important migration rule is: never call referrals.convert for historical conversions. Conversion is a live business action that issues fresh rewards.

1. Choose the cutover policy

Decide whether you will:

• preserve existing code strings or issue new OfferKit codes;
• keep legacy rewards redeemable in the old system;
• import still-active legacy reward vouchers into OfferKit;
• preserve original order or event IDs for reconciliation;
• run a hard cutover or a short period of dual reads.

Document a timestamp after which every new conversion belongs to OfferKit.

2. Import customers first

Every advocate and referred customer needs an OfferKit customer. Upsert using your stable user ID as externalId and build a mapping to the returned OfferKit IDs. This step is idempotent and safe to rerun.

3. Import advocate codes

referrals.issue safely creates or fetches one code per (programId, customerId), but it generates the code string. Use it when issuing new codes is acceptable.

If existing strings must remain valid, perform a controlled database import into referral_code. Validate global uniqueness first and use conflict guards on program and customer. Take a database backup and rehearse the import in staging.

4. Import conversions as history

Insert historical referral_conversion rows directly rather than calling the live conversion endpoint. Preserve:

• the advocate code association;
• referred customer ID;
• converted timestamp;
• original order or event ID;
• reward outcome references when they remain meaningful.

Use uniqueness constraints and ON CONFLICT guards so the importer is safe to rerun.

5. Decide what happens to old rewards

• If rewards were already used, keep only the historical conversion evidence.
• If the old system still honors active rewards, let it remain their source of truth.
• If OfferKit must honor them, create equivalent OfferKit vouchers with the original codes and connect the imported outcomes deliberately.

Avoid mirroring the same active reward into two systems.

6. Verify before cutover

Compare counts for imported customers, codes, and conversions. Spot-check records across old and recent dates. Verify that a known historical conversion cannot issue rewards again.

Then test one new conversion end to end through Launch a referral program. Keep the legacy data read-only for an agreed retention period so reconciliation remains possible.

The original low-level SQL migration walkthrough remains available at the legacy referral migration reference.