02 — The Engineering Choices
Built like a retention stack: route, cache, measure.
The same discipline I'd apply to an ESP bill applies to an API bill. Three choices keep the pipeline fast and cheap without giving up quality where it matters.
Model Tiering
Every agent runs on the cheapest model that does its job well
Content that a human will read (resume bullets, critiques, outreach) runs on Opus. Research, scoring, and scaffolding run on Sonnet at 60% of the input cost. The routing lives in one config line per agent, so when a smaller model gets good enough, the swap is a one-word change — the code comments literally note which tiers are next in line for a downgrade test.
Prompt Caching
Shared context is written once, cached, and reused — cached reads cost ~10% of fresh input
My resume, profile, and each step's system prompt are marked as cacheable prefixes. The critique step is the showcase: the full teardown context is cached on the first persona pass, and the CEO, CMO, and hiring-manager reads all hit the same cache. Stable content up front, dynamic content last — the same rule that makes email templates cacheable in an ESP.
Cost Telemetry
Every call logs tokens, cache hit rate, and dollars — and low hit rates get flagged automatically
Each API call appends a labeled row to a usage log; a report script aggregates cost per step and flags any label with a cache hit rate under 20% — the usual culprit being a timestamp near the top of a prompt breaking the prefix match. It's the same instinct as monitoring deliverability: you don't find out something broke from the invoice.
Why this is on a marketing portfolio
Lifecycle marketing is becoming an orchestration job — this is what my orchestration looks like.
Segmentation, routing, suppression, cost-per-touch, instrumentation: the concepts that make a lifecycle program work are the same ones that make an AI pipeline work. I'd rather show working code than claim "AI-curious" on a resume. The system produced the applications, the teardowns on this site, and the outreach that got them read.