System Design Skill

Purpose

Enable the Solution Architect Agent to design the high-level structure of software systems, selecting appropriate patterns, technologies, and integration strategies.

Architectural Patterns

1. Monolithic

• Use Case: Small startup, simple domain, fast initial dev.
• Pros: Simple deployment, easy debugging.
• Cons: Scalability limits, tight coupling.

2. Microservices

• Use Case: Complex enterprise, distinct domains, independent scaling.
• Pros: Tech stack agnostic per service, scalable.
• Cons: Distributed complexity, network latency, data consistency.

3. Event-Driven

• Use Case: Real-time interactions, high decoupling.
• Components: Producers, Consumers, Event Bus (Kafka, RabbitMQ).

4. Serverless

• Use Case: Event-triggered, variable load.
• Pros: Pay-per-use, no infra management.

Key Design Decisions (The "ilities")

• Scalability: Vertical (bigger machine) vs. Horizontal (more machines).
• Availability: Redundancy, failover strategies. Load balancers.
• Reliability: Circuit breakers, retries, eventual consistency.
• Maintainability: Clean code, documentation, monitoring.
• Security: Authentication (OAuth), Authorization (RBAC), Encryption.

API Design Strategy

• REST: Standard resource-based.
• GraphQL: Flexible data querying.
• gRPC: High performance inter-service comms.

Database Selection

• Relational (SQL): Structured data, ACID transactions (PostgreSQL, MySQL).
• NoSQL (Document): Flexible schema, rapid iteration (MongoDB).
• NoSQL (Key-Value): Caching, heavy read/write (Redis, DynamoDB).
• Time-Series: IoT, financial data (InfluxDB).

Documenting Architecture

• C4 Model: Context, Container, Component, Code.
• ADR (Architecture Decision Records): Documenting WHY a decision was made.

Deliverables

• High-Level Design (HLD) Document.
• Low-Level Design (LLD) Document.
• Database Schema (ERD).
• API Specifications (Swagger/OpenAPI).