Architecture And Stack

05 — Architecture and Stack

Default stack: _kernel/standards.md#stack. Override conditions below.

Cloudflare-first decision tree

Compute: Workers (default, every HTTP/cron/queue) · Pages (static-only marketing, rare) · Containers (non-JS runtimes: Playwright headful, ffmpeg, Python ML, build orchestration) · Sandbox SDK (generated/risky code before live promotion)

State: D1 (default relational, ≤10GB/db, Sessions API read-replicas, Time Travel 30-day PIT) · KV (eventually-consistent, cache/sessions/feature-flags) · R2 (object storage, lifecycle Standard→IA after 30d) · Durable Objects (coordination + strongly-consistent SQLite storage since Apr 2025, chat rooms/builder sessions/rate-limiting) · Hyperdrive (front external Postgres/MySQL) · Vectorize (semantic search/RAG, 5M dim/index, topK 100, 10 metadata indexes)

Async: Queues (best-effort, 5000 msg/sec, R2 event notifications) · Workflows v2 (deterministic, 50K concurrent, 300 creates/sec, 2M queued/workflow, step.do + step.sleep + step.waitForEvent) · Inngest (event-driven, better DX/observability)

AI: Workers AI (Llama 3.3 70B FP8 free, Llama 3.1 8B FP8, Llama 4 Scout 17B vision) · AI Gateway (caching + rate-limit + fallback + logging for every LLM call) · Vectorize (embeddings + ANN search)

Override conditions (when CF isn't enough)

Adapters live in libs/core/ports/. Product code imports port, never vendor SDK directly. See rules/cloudflare-hostable-supervisor.md.

Auth (default Clerk M2M JWT)

• Clerk — M2M JWT (free, networkless verification), passkeys, OAuth, magic links; Better Auth when Clerk pricing doesn't fit (rare)
• Hash API keys at rest. Audit log every sensitive action.
• Tenant isolation: every table carries org_id, every query filters by it (404 on mismatch, never 403)

Data patterns

D1

[[d1_databases]]
binding = "DB"
database_name = "myapp"

• wrangler types against compatibility_date + bindings (preferred over hand-maintained Env interface)
• Drizzle v1 RQBv2 + Zod for query + validation; batch via db.batch([...]) (no transactions in D1)
• Sessions API: db.withSession(bookmark) · Time Travel: wrangler d1 time-travel restore

R2: per-extension content-type on upload · lifecycle Standard→IA after 30d · event notifications → Queues at 5000 msg/sec for thumbnailing/indexing · versioning for asset rollback

Durable Objects: one DO per stateful entity · SQLite-backed, 10GB per DO · direct stub env.MY_DO.getByName(name) · alarm misfires → idempotent handler

Reliability

• Workers CPU 10ms free / 50ms paid default (configurable 5min); wall time 30s paid
• ctx.waitUntil() for async post-response work; ctx.passThroughOnException() for graceful degradation
• WebSocket + JSRPC payload up to 32 MiB

Cost discipline

• Workers free tier: 100k req/day; Workers Paid: $5/mo (10M req + 30M CPU-ms) + $0.30/M extra req + $0.02/M extra CPU-ms
• D1 on Workers Paid: 5GB + 25B rows-read + 50M rows-written/mo; then $0.75/GB-mo + $0.001/M rows-read + $1/M rows-written; no egress; read replication included (verified 2026-06-09)
• R2: 10GB free, $0.015/GB-mo, $0/egress · Workers AI Llama 3.3 70B FP8 FREE · AI Gateway free
• Solo SaaS <$100k/mo MRR stays 10-100× cheaper than AWS-equivalent on CF

Default config (wrangler.jsonc)

{
  "name": "myapp",
  "main": "src/worker/index.ts",
  "compatibility_date": "2026-04-15",
  "compatibility_flags": ["nodejs_compat"],
  "observability": { "enabled": true },
  "secrets_required": ["CLERK_SECRET_KEY", "RESEND_API_KEY"],
  "d1_databases": [{ "binding": "DB", "database_name": "myapp" }],
  "kv_namespaces": [{ "binding": "CACHE", "id": "..." }],
  "r2_buckets": [{ "binding": "BUCKET", "bucket_name": "myapp-assets" }],
  "ai": { "binding": "AI" }
}

Decision template (use for every architecture call)

1. Can CF primitive do this? → Use it.
2. Does this need adapter for portability? → Adapter only if real business case.
3. Cost projection at 10× current scale → Still affordable?
4. Failure mode → Graceful degradation defined?
5. Migration path → If we have to leave CF, what does it cost?

See submodules: cloudflare-primitives.md, data-patterns.md, reliability.md, auth-patterns.md.