Temporal

# MISSION: Scaffold "Temporal" Production Architecture
You are an expert Senior Staff Software Architect and Full-Stack Engineer. Your mission is to scaffold and implement a production-grade, highly reliable, and modular codebase following the proven architecture of **Temporal**.
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## 1. PROJECT SPECIFICATIONS & BENCHMARK
- **Reference Architecture**: Temporal
- **What It Does**: Open-source durable execution platform and distributed workflow orchestrator built in Go.
- **Domain & Category**: Distributed Workflow Orchestrator
- **Production Scale**: 20+ People
- **Development Mode**: CLASSIC
- **Architectural Rationale**: Temporal keeps workflow code in external workers and persists every state transition as an event history that the Go gRPC cluster (Frontend, History and Matching services) replays after crashes or restarts, so long-running workflows survive failures on PostgreSQL, MySQL, SQLite or Cassandra storage.
- **Live Website Reference**: https://temporal.io
- **Source Repository**: https://github.com/temporalio/temporal
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## 2. PRODUCTION TECH STACK
- **Full Stack Array**: Temporal, Go, PostgreSQL, Cassandra, Elasticsearch, Prometheus, OpenTelemetry
- **Primary Language(s)**: Go, Shell, PLpgSQL, Makefile, CQL, Go Template
- **License of the reference repo**: MIT
- **Backend & APIs**: Temporal — Core durable execution and distributed workflow orchestration platform; Go — Primary systems language powering internal microservices and state transitions
- **Data & persistence**: PostgreSQL — Relational persistence layer storing workflow execution history and task queues; Cassandra — Distributed NoSQL persistence driver for high-throughput clustered deployments; Elasticsearch — Advanced visibility query engine supporting custom search attributes
- **Infrastructure & deploy**: Prometheus — Native metrics instrumentation and scrape endpoint exporter; OpenTelemetry — End-to-end distributed tracing across gRPC RPC boundaries and activity dispatches
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## 3. KEY ARCHITECTURAL DECISIONS (audited from https://github.com/temporalio/temporal @ 9bab3d8)
1. **Event Sourced Durable Execution Engine**: Preserves deterministic workflow execution state as an append-only sequence of event history records, enabling full recovery across hardware failures.
2. **Service Decomposition into Four Internal Roles**: Splits server processes into Frontend, History, Matching, and Worker services that can be scaled horizontally and deployed independently.
3. **Pluggable Multi-Database Persistence Layer**: Uses database abstraction adapters supporting PostgreSQL, MySQL, SQLite, and Apache Cassandra through unified transaction interfaces.
4. **Nexus RPC Integration for Cross-Cluster Workflows**: Adopts the Nexus RPC standard to coordinate long-running distributed operations across organizational boundaries and multi-region clusters.
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## 4. NON-NEGOTIABLE ARCHITECTURAL GUARDRAILS
1. **Monorepo & Modular Separation**:
   - Structure as a Turborepo monorepo with strict package boundaries:
     - `apps/web`: Application UI, routing, layouts, and server endpoints.
     - `packages/ui`: Shared design tokens, CSS variables, and Radix UI primitive components.
     - `packages/db`: Database schemas, client singleton, declarative migrations, and seed scripts.
     - `packages/config`: Shared TypeScript, ESLint, and build configurations.
2. **Strict Type Safety & Zero `any` Policy**:
   - Enable `strict: true`, `noImplicitAny: true`, and `strictNullChecks: true`.
   - Validate ALL external inputs, API request bodies, and query parameters with **Zod** schemas before execution.
3. **Frontend & Rendering Guidelines**:
   - Isolate interactive UI state to leaf components. Keep core pages lightweight and performant.
4. **Design System & Aesthetics**:
   - Keep every color, radius, shadow and font in a single token file (CSS variables) and consume tokens everywhere; never hardcode hex values in components.
   - Prefer crisp 1px borders and one subtle shadow scale over blurry default shadows. Pair one sans-serif for body/headings with one monospace for tags, badges, metrics, and code.
5. **Data Layer & Reliability**:
   - Write declarative schema definitions with foreign keys, composite indexes on queried filters, and automated timestamp triggers.
   - Use connection pooling and prepared statements for serverless database execution.
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## 5. STEP-BY-STEP SCAFFOLDING ROADMAP
- **Phase 1: Workspace & Root Config**: Initialize package manager, monorepo configuration (`turbo.json`, `tsconfig.base.json`, `package.json`).
- **Phase 2: Database Schema & Client**: Set up the data layer (PostgreSQL, Cassandra, Elasticsearch): client, connection pool, models, and migration scripts.
- **Phase 3: Design Tokens & UI Primitives**: Build accessible `Button`, `Input`, `Card`, `Badge`, and layout wrappers inside `packages/ui`.
- **Phase 4: Core Application Routes & Handlers**: Implement primary authentication, user session handling, and application routes.
- **Phase 5: Quality Assurance & Build Verification**: Run `tsc --noEmit`, ESLint, Prettier, and smoke test suites to ensure zero compilation or runtime errors.
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## 6. EXECUTION INSTRUCTIONS
1. Review all specifications, architectural guardrails, and stack choices above.
2. Present the full monorepo directory tree structure.
3. Systematically generate the complete, production-ready codebase according to the 5-phase roadmap above — starting with the root workspace setup, followed by the database schema, UI design system package, and full-stack application routes until the repository is fully scaffolded and ready to run.