Architectural Planning

Interactively guide the user through architectural decisions for a new or existing software project. Asks structured questions to understand requirements, recommends compatible technologies for each layer, and generates a comprehensive architecture document with Mermaid diagrams, component breakdowns, and a recommended project directory layout.

Approach: Step-by-step interactive questionnaire using AskUserQuestion, with technology-specific suggestions informed by the compatibility matrices in references/architectural-planning-reference.md. The final output is a single Markdown document with embedded Mermaid architecture and deployment diagrams.

Prerequisites

• No tools or dependencies required
• Works for any project type (greenfield or existing)
• Requires interactive session (AskUserQuestion must be available)

Workflow

Step 1 — Understand the Project

Use AskUserQuestion to ask the following. Ask both questions in a single AskUserQuestion call (multi-question).

Question 1 — Project Type:

What type of project are you building?

Options:

1. API / Backend only — REST API, GraphQL server, or gRPC service with no UI
2. Frontend only — SPA or static site consuming an existing API
3. Full-stack web application — Backend + frontend in one project
4. Microservices — Multiple independent services communicating via APIs or events
5. CLI tool / Library — Command-line application or reusable package
6. Mobile backend — API optimized for mobile clients (BFF pattern)

Question 2 — Expected Scale:

What is the expected scale of this project?

Options:

1. Small / Personal — Single developer, <1K users, simple deployment
2. Startup / Team — 2-10 developers, 1K-100K users, need to iterate fast
3. Enterprise / Large — 10+ developers, 100K+ users, high availability required

Store both answers as project_type and project_scale — these determine which follow-up steps to ask and which technologies to recommend.

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Step 2 — Choose Backend Stack

Skip this step if project_type is "Frontend only".

Read references/architectural-planning-reference.md Section 1 (Backend Stack Matrix) for detailed comparison.

Use AskUserQuestion:

Which backend technology stack do you prefer?

Options (include "Best for" from the reference):

1. Java / Spring Boot — Enterprise-grade, strong typing, huge ecosystem. Best for: large teams, microservices, enterprise integrations.
2. Node.js / Express — Fast iteration, JavaScript everywhere, massive npm ecosystem. Best for: startups, real-time apps, full-stack JS teams.
3. Python / Django — Batteries included, rapid prototyping, excellent admin panel. Best for: MVPs, admin-heavy apps, ML/data projects.
4. Python / FastAPI — Modern async Python, auto-generated OpenAPI docs, high performance. Best for: APIs, microservices, ML model serving.

Present the remaining options if the user selects "Other" or based on scale:

• Go — High performance, built-in concurrency, small binaries. Best for: microservices, infrastructure tools, high-throughput APIs.
• .NET / ASP.NET Core — Enterprise framework, excellent tooling, cross-platform. Best for: enterprise apps, Windows ecosystem.
• Rust / Actix-web — Maximum performance and safety. Best for: performance-critical services, systems programming.

Store as backend_stack.

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Step 3 — Choose Frontend Stack

Skip this step if project_type is "API / Backend only", "CLI tool / Library", or "Mobile backend".

For "Microservices", ask if any service has a frontend before presenting options.

Use AskUserQuestion:

Which frontend framework do you prefer?

Options:

1. React — Component-based, largest ecosystem, flexible. Pairs with: Next.js (SSR), Vite (SPA).
2. Vue.js — Gentle learning curve, progressive framework. Pairs with: Nuxt (SSR), Vite.
3. Angular — Full framework, TypeScript-first, strong opinions. Best for: enterprise, large teams.
4. Svelte / SvelteKit — Compile-time framework, minimal runtime. Best for: performance-focused apps.

Additional options if needed:

• Next.js (React) — Full-stack React with SSR/SSG/ISR. Best for: SEO, marketing sites.
• HTMX + server templates — Minimal JavaScript, server-rendered. Best for: simple UIs.
• Server-rendered templates only — Jinja2, Thymeleaf, Razor, etc. (no separate frontend)

Store as frontend_stack. If skipped, set to "N/A".

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Step 4 — Choose Database and Data Layer

Skip this step if project_type is "Frontend only".

Read references/architectural-planning-reference.md Section 2 (Database Compatibility Matrix) to present options compatible with backend_stack.

Use AskUserQuestion:

What are your data storage needs?

Options:

1. PostgreSQL — Relational, ACID, JSON support, full-text search. The safe default for most projects.
2. MySQL / MariaDB — Relational, widely supported, simpler than PostgreSQL.
3. MongoDB — Document store, flexible schema. Good for rapid prototyping and varied data shapes.
4. SQL Server — Enterprise relational, deep .NET integration, strong BI tooling.

Additional options:

• DynamoDB — AWS-native NoSQL, auto-scaling. Best for: serverless, high-scale key-value.
• SQLite — Embedded, zero-config, single-file. Best for: small apps, local-first, testing.
• Redis (as primary) — In-memory data store for specific use cases (sessions, leaderboards).
• Multiple — Need both relational and NoSQL

After the user chooses, immediately recommend the compatible ORM / data-access library from the reference file's Database Compatibility Matrix for their backend_stack + database combination. Present it as an informational message, e.g.:

For Spring Boot + PostgreSQL, the recommended data access stack is:

• ORM: Spring Data JPA + Hibernate
• Connection pool: HikariCP (included by default)
• Migrations: Flyway

These are the standard choices and work seamlessly together.

Also recommend the migration tool from the Migration Tools table.

Store as database, data_access_library, and migration_tool.

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Step 5 — Choose Caching Strategy

Use AskUserQuestion:

Do you need a caching layer?

Options:

1. Redis — Distributed cache, pub/sub, data structures. Industry standard for multi-instance apps.
2. Memcached — Simple distributed cache, fast, lightweight. Best for: pure key-value caching.
3. In-memory only — Application-level cache (e.g., Caffeine for Java, node-cache for Node.js, lru_cache for Python). Best for: single-instance apps.
4. No caching needed — Skip for now

Additional options:

• CDN caching — Edge caching for static assets and API responses (CloudFront, Cloudflare, Fastly).
• Multi-layer — Combine in-memory + distributed + CDN

After the user chooses, recommend the specific library from references/architectural-planning-reference.md Section 3 (Caching Library Matrix) for their backend_stack + caching combination.

Store as caching_strategy and cache_library.

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Step 6 — Choose Authentication and Authorization

Skip this step if project_type is "CLI tool / Library".

Use AskUserQuestion:

How will you handle authentication?

Options:

1. JWT tokens — Stateless auth, good for APIs and SPAs. Implement with framework-native libraries.
2. Session-based — Server-side sessions with cookies. Traditional, simpler for server-rendered apps.
3. OAuth 2.0 / OpenID Connect — Delegate to identity providers (Google, GitHub, etc.).
4. Managed service (Auth0 / Firebase / Cognito) — Offload auth complexity entirely.

Additional options:

• Keycloak — Self-hosted identity server. Best for: enterprise, on-prem, full control.
• API keys — Simple key-based auth for service-to-service or public APIs.
• Framework built-in — Use the framework's native auth (Django Auth, Spring Security, ASP.NET Identity)

After the user chooses, recommend the specific library from references/architectural-planning-reference.md Section 4 (Authentication Library Matrix) for their backend_stack + auth combination.

Store as auth_approach and auth_library.

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Step 7 — Choose Messaging and Events

Skip this step if project_scale is "Small / Personal" AND project_type is NOT "Microservices".

Use AskUserQuestion:

Do you need asynchronous messaging or event-driven communication?

Options:

1. Apache Kafka — High-throughput event streaming, durable log. Best for: event sourcing, data pipelines.
2. RabbitMQ — Traditional message broker, flexible routing. Best for: task queues, RPC patterns.
3. AWS SQS / SNS — Managed queues and pub/sub. Best for: AWS-native, serverless.
4. No messaging needed — Skip for now

Additional options:

• Redis Pub/Sub — Lightweight pub/sub for simple real-time notifications.
• NATS — Lightweight, high-performance. Best for: microservices, cloud-native.

Store as messaging. If skipped, set to "None".

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Step 8 — Choose Deployment Strategy

Use AskUserQuestion. Ask both in a single call.

Question 1 — Deployment:

How do you plan to deploy?

Options:

1. Docker + Kubernetes — Container orchestration, auto-scaling. Best for: microservices, large-scale.
2. Docker + Docker Compose — Simple container deployment. Best for: small teams, single-server.
3. Serverless — AWS Lambda / Azure Functions / GCP Cloud Functions. Best for: event-driven, pay-per-use.
4. PaaS — Heroku, Railway, Render, Fly.io. Best for: rapid deployment, no infra management.

Additional options:

• Traditional VM / VPS — EC2, DigitalOcean, Linode. Best for: full control, predictable costs.
• Cloud-managed containers — AWS ECS/Fargate, Azure Container Apps, GCP Cloud Run.
• Edge deployment — Cloudflare Workers, Vercel Edge, Deno Deploy.

Question 2 — Cloud Provider:

Which cloud provider (if any)?

Options:

1. AWS 2. Azure 3. Google Cloud 4. No preference / Self-hosted

Store as deployment and cloud_provider.

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Step 9 — Choose CI/CD Pipeline

Use AskUserQuestion:

What CI/CD platform do you prefer?

Options:

1. GitHub Actions — Native to GitHub, free for public repos, huge marketplace.
2. GitLab CI — Built into GitLab, powerful pipelines, self-hostable.
3. Jenkins — Self-hosted, extensible, enterprise standard.
4. Other / No preference — CircleCI, AWS CodePipeline, Azure DevOps, etc.

Store as cicd.

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Step 10 — Choose Monitoring and Observability

Use AskUserQuestion:

What monitoring and observability tools do you want?

Options:

1. Datadog — Full-stack observability (metrics, traces, logs). Enterprise standard.
2. Prometheus + Grafana — Open-source metrics and dashboards. Best for: self-hosted, Kubernetes.
3. Cloud-native — AWS CloudWatch / Azure Monitor / GCP Cloud Monitoring.
4. Basic logging only — Framework-native logging, no external tools for now.

Additional options:

• ELK Stack — Open-source log aggregation and analysis.
• OpenTelemetry + Jaeger — Vendor-neutral distributed tracing.
• Sentry — Error tracking and performance monitoring.
• Multiple — Combine (e.g., Prometheus for metrics + ELK for logs + Sentry for errors)

Store as monitoring.

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Step 11 — Confirm and Generate

11a. Present the decision summary. Display a table of all decisions made:

| Layer              | Choice                    |
|--------------------|---------------------------|
| Project Type       | {project_type}            |
| Scale              | {project_scale}           |
| Backend            | {backend_stack}           |
| Frontend           | {frontend_stack}          |
| Database           | {database}                |
| ORM / Data Access  | {data_access_library}     |
| Migrations         | {migration_tool}          |
| Caching            | {caching_strategy}        |
| Authentication     | {auth_approach}           |
| Messaging          | {messaging}               |
| Deployment         | {deployment}              |
| Cloud Provider     | {cloud_provider}          |
| CI/CD              | {cicd}                    |
| Monitoring         | {monitoring}              |

11b. Ask for confirmation. Use AskUserQuestion:

Here is your architecture summary. What would you like to do?

Options:

1. Generate the architecture document — Proceed to output
2. Change a decision — Go back and modify a choice
3. Add more detail — Discuss specific areas further before generating

If "Change a decision", ask which layer to change and re-run that step.

11c. Ask for output location. Use AskUserQuestion:

Where should I write the architecture document?

Options:

1. ARCHITECTURE.md — In the project root (recommended)
2. .architecture/architecture-{timestamp}.md — In a dedicated directory
3. Custom path — Specify a path

11d. Generate the document. Read the output document template from references/architectural-planning-reference.md Section 6 and generate the full architecture document:

1. Replace all {PLACEHOLDER} values with the user's actual choices
2. Select the appropriate Mermaid diagram from Section 5 based on project_type and customize it with actual technology names
3. Select the project structure from Section 7 based on backend_stack
4. Build the dependency table from Section 8 (Library Version Reference) for the chosen stack
5. Customize all 11 sections of the document with specific, actionable content
6. Scale the document depth based on project_scale — simpler projects get more concise sections, enterprise projects get more detailed coverage

Write the generated document to the chosen path using the Write tool. If using the .architecture/ directory, create it first.

11e. Present the result. Tell the user the document has been written and summarize the key architectural decisions. Offer to dive deeper into any specific section.

Additional Resources

• references/architectural-planning-reference.md — Technology compatibility matrices (backend × database, backend × cache, backend × auth), Mermaid diagram templates for monolith/microservices/serverless/deployment topologies, complete output document template with 11 sections, project structure templates per stack, and library version reference