Vectorspace Adserver

The Vector Space series is the spec. The source code is the artifact, live at vectorspace.exchange: generated from those posts with a coding agent. This post covers the engineering decisions that didn’t warrant their own post, the ones you’d only find by reading the code.

Decisions that didn’t warrant their own post but would feel wrong if missing:

• Vendored enclave. Auction math is vendored into a standalone repo so auditors can clone, build, and hash without ambiguity. auction_crosscheck_test.go asserts bit-identical results between copies. Auction mechanism from CloudX OpenAuction. See Attested Attribution.
• Intent extraction prompt. “Write as if the provider were writing their own position statement.” Maps user chat into the same semantic frame as advertiser positioning. Runs on the publisher’s LLM, not the exchange’s.
• Publisher skills instead of an SDK. Four prompt documents a coding agent reads to evaluate, install, verify, and uninstall the integration. No package dependency. The agent writes code directly into the publisher’s files and opens a PR.
• Ciphertext pass-through. The SDK encrypts the embedding with the enclave’s attested public key. The server passes ciphertext it can’t read to the TEE via vsock. Plaintext embeddings get rejected with 400. The exchange never sees the query. See process.go.
• CPC billing. VCG payment computed at auction time, charged on first click. events table deduplicates: one charge per auction, no matter how many clicks. See One-Shot Bidding.
• Per-auction receipts. Both sides pull their own records: GET /portal/auctions for advertisers, GET /portal/publisher/auctions for publishers. Every auction individually queryable with exact VCG payment. See Receipts, Please.
• Creatives decoupled from position. Position (embedding + σ + bid) is the auction identity. Creative (title + subtitle) is what the user sees. A/B test creatives without moving your position. Position changes cost a relocation fee; creative changes are free.
• Content-addressed positions. SHA-256 hash of all positions returned as ETag. SDK sends If-None-Match, gets 304 if nothing changed. Negligible polling cost.
• Pulumi in Go for infrastructure. EC2 + Docker Compose + EBS for SQLite persistence + S3/CloudFront for the landing page + Route 53 + ACM cert. One command to stand up the whole stack.
• Embedding service as a separate container wrapping BGE-small-en-v1.5, or Hugging Face Inference API if you set HF_TOKEN. Swap the model without touching the auction server.
• Multi-stage Docker builds. Go server and Node portal compile in build stages, ship on Alpine. Embedding service pre-downloads the model at build time so cold starts don’t hit a model registry.
• Makefile with make dev, make test, make deploy. Clone, one command, auctions running.
• Frozen lockfiles everywhere. go.sum, pnpm-lock.yaml, uv.lock. Builds are reproducible or they don’t ship.
• Caddy for TLS termination and reverse proxy. Auto-renews certificates. Zero config beyond a Caddyfile.
• Frequency capping. 3 impressions per advertiser per user per 60-minute window. SDK gets 429 when capped.

The blog series is the spec. The repo was built from it with Claude Opus 4.6 via Claude Code.

Part of the Vector Space series.