Sabermatic

System-design interview practice with an AI coach. Voice-driven, real-time, structured feedback.

Try it: sabermatic.dev

This repo's git slug is drill (project codename); the product is Sabermatic.

License

Sabermatic is released under the Functional Source License, Version 1.1, Apache 2.0 Future License. You may read, fork, run, modify, and learn from the code. You may not run it as a competing service. This release converts to Apache 2.0 on 2028-05-05; subsequent releases convert two years after their publication.

Why this exists

Sabermatic was built end-to-end with Claude Code over ~6 weeks. The docs/superpowers/specs/ and docs/superpowers/plans/ directories show every feature's spec → plan → implementation cycle in real use. CLAUDE.md documents the project's engineering conventions. Source-available because we want the workflow and the code to be readable, but not trivially clonable as a competing service.

Architecture

flowchart LR
  Browser[Browser - React/Vite] -->|ConnectRPC| API[Go API - Cloud Run]
  Browser -.->|audio via server-stream| API
  API --> DB[(Postgres - Cloud SQL)]
  API --> SM[GCP Secret Manager]
  API --> LLM[Anthropic / OpenAI]
  API --> Stripe[Stripe Billing]
  API -->|stderr logs| BQ[(BigQuery analytics)]

Loading

• Backend: Go 1.25, ConnectRPC, sqlc, River jobs, Postgres 16, OpenTelemetry.
• Frontend: React 19, Vite, Tailwind, ConnectRPC client.
• Infra: GCP Cloud Run, Cloud SQL, Secret Manager, Artifact Registry, BigQuery. Terraform-managed.
• Billing: Stripe (subscriptions + minute packs).

Repository layout

Path	Purpose
internal/	Backend Go code (handlers, services, jobs, db, billing).
cmd/	Binaries (drill, drillctl, stripescenario).
web/	React frontend.
pb/	Protobuf source (.proto); generated code in internal/pb/ and web/src/pb/.
sql/	Database migrations and sqlc queries.
terraform/	GCP infrastructure as code.
docs/	Engineering specs, plans, and reference docs.
CLAUDE.md	Conventions for AI-assisted development in this repo.

Running locally

Prerequisites

• Go 1.25 (see go.mod)
• Node 22 (see .nvmrc)
• Postgres 16
• (Optional) Docker, for ancillary services

Quickstart

git clone https://github.com/btc/sabermatic.dev.git
cd drill
cp .env.example .env
# Populate .env per the comments inside it
make dev

make dev starts the Vite dev server and the Go backend (with hot reload via air) on port :8080.

See .env.example for every key the backend reads. Some keys are only needed for specific features:

• LLM features require ANTHROPIC_API_KEY (and optionally OPENAI_API_KEY).
• Stripe billing requires the STRIPE_* keys plus make stripe-setup to populate STRIPE_WEBHOOK_SECRET.
• GCP Secret Manager is a no-op locally; the backend reads from .env instead.
• BigQuery analytics (event sink) requires a deployed environment.
• OAuth (Google, GitHub) requires registered client IDs/secrets.

Testing

make test

Runs: buf lint, codegen check, go test ./internal/... ./cmd/... -race -count=1, golangci-lint, frontend tsc --noEmit -p tsconfig.app.json, ESLint, Vitest. CI runs the same target.

Deployment

See terraform/ for the GCP infrastructure that backs production. scripts/deploy.sh triggers a Cloud Run deploy.

Contributing

Sabermatic is source-available, not open source. We are not currently accepting outside pull requests, but bug reports via Issues are welcome.