Buyer ID Synchronization

[aram356]

Problem Statement

Today, Trusted Server (TS) generates privacy-preserving synthetic IDs for users but has no mechanism to link these IDs to buyer-side identifiers. When TS sends bid requests to demand partners (DSPs/SSPs) via Prebid Server, buyers cannot match the request to their own user profiles. This results in lower bid rates, reduced CPMs, and lost revenue — buyers are effectively bidding blind.

Goal

Enable buyers to synchronize their own user identifiers with TS synthetic IDs so that:

• Bid requests carry buyer-recognized IDs, improving match rates and bid quality
• The privacy-preserving architecture is maintained — buyer IDs are resolved server-side, never exposed to the browser
• The system follows IAB OpenRTB standards for interoperability with the broader programmatic ecosystem

Value Statement

As a buyer, I want to upload my user identifiers mapped to TS synthetic IDs, so that when TS sends me bid requests, I can recognize the user and bid with higher confidence and relevance.

As a publisher, I want TS to enrich bid requests with buyer-recognized IDs, so that buyers bid higher CPMs and I earn more revenue.

Non-Functional Requirements

Requirement	Detail
Latency	KV lookup must add < 2ms to auction path
Data leakage	Buyer IDs are resolved server-side only; never sent to the browser ( is this possible?)
Standards	Uses IAB OpenRTB 2.6 user.eids for buyer ID transport
Availability	KV lookup failures must not block auctions
Security	Batch upload API must require authentication
Scalability	Must handle batch uploads of up to 1000+ records per request

Dependencies

• Fastly KV Store provisioning for the new id_sync_store
• Prebid Server must be configured to accept and route user.eids to bidder adapters
• Buyers need access to synthetic IDs (currently returned in auction response headers: X-Synthetic-ID)

Out of Scope (Future Considerations)

• Automatic extraction of buyer IDs from Prebid Server responses
• Real-time single-record sync API (vs batch)
• TTL/expiration policies for stale mappings
• Multi-publisher ID graph federation
• Buyer-side dashboard for sync status monitoring