trd

name	trd
description	Use when writing Technical Requirements Documents that define how to build a system. Covers system architecture, API specifications, data models, security requirements, performance requirements, dependencies, technical constraints, and deployment plans. USE FOR: technical design specifications, API contracts, data model documentation, system architecture descriptions, performance and security requirements, deployment plans, infrastructure requirements, technical constraints documentation DO NOT USE FOR: product-level requirements (use prd), business justification (use brd), recording individual decisions (use adr), executable specs (use gherkin or gauge)
license	MIT
metadata	{"displayName":"TRD (Technical Requirements Document)","author":"Tyler-R-Kendrick"}
compatibility	claude, copilot, cursor
references	[{"title":"Software Requirements Specification — Wikipedia","url":"https://en.wikipedia.org/wiki/Software_requirements_specification"}]

Technical Requirements Document (TRD)

Overview

A Technical Requirements Document (TRD) defines how a system or feature will be built. It translates the product requirements from the PRD into concrete technical specifications -- architecture, APIs, data models, security controls, performance targets, and deployment strategy. The TRD is the engineering team's blueprint for implementation.

The TRD sits downstream of the PRD and upstream of implementation:

PRD ("What are we building?") --> TRD ("How do we build it?") --> Implementation + ADRs

Standard TRD Structure

1. Title and Metadata

Document identification, ownership, and status tracking.

2. System Overview

High-level description of the system, its purpose, and how it fits into the broader architecture.

3. Architecture

System architecture including components, interactions, technology stack, and diagrams.

4. API Specifications

Endpoints, request/response schemas, authentication, error handling, and versioning.

5. Data Models

Database schema, entity relationships, data types, constraints, and migration strategy.

6. Security Requirements

Authentication, authorization, encryption, compliance, and threat model.

7. Performance Requirements

Latency, throughput, availability, and scalability targets.

8. Dependencies

External services, libraries, infrastructure, and team dependencies.

9. Technical Constraints

Technology mandates, backward compatibility, regulatory, and organizational constraints.

10. Deployment Plan

Environments, CI/CD pipeline, rollout strategy, and rollback procedures.

Complete TRD Template

# TRD: [System/Feature Name]

| Field            | Value                          |
|------------------|--------------------------------|
| Author           | [Name]                         |
| Status           | Draft / In Review / Approved   |
| Created          | YYYY-MM-DD                     |
| Last Updated     | YYYY-MM-DD                     |
| PRD Reference    | [Link to PRD]                  |
| Reviewers        | [Names]                        |
| Approvers        | [Names]                        |

## 1. System Overview

### 1.1 Purpose
[Brief description of what this system does and why it exists.
Reference the PRD for product context.]

### 1.2 Scope
[What is covered by this TRD. What is explicitly excluded.]

### 1.3 Context
[How this system fits into the broader architecture.
Include a C4 Context diagram or equivalent.]

```mermaid
graph LR
    User[End User] --> WebApp[Web Application]
    WebApp --> API[API Gateway]
    API --> AuthService[Auth Service]
    API --> OrderService[Order Service]
    OrderService --> Database[(PostgreSQL)]
    OrderService --> MessageQueue[RabbitMQ]
    MessageQueue --> NotificationService[Notification Service]

2. Architecture

2.1 Architecture Style

[Monolith / Microservices / Serverless / Event-driven / Hybrid] [Justification for the chosen approach. Link to ADR if applicable.]

2.2 Component Overview

Component	Responsibility	Technology
API Gateway	Request routing, rate limiting, auth	[e.g., Kong]
Auth Service	Authentication, token management	[e.g., .NET 8]
Order Service	Order lifecycle management	[e.g., .NET 8]
Notification Service	Email, SMS, push notifications	[e.g., Node.js]
Database	Persistent data storage	[e.g., PostgreSQL]
Message Queue	Async event processing	[e.g., RabbitMQ]

2.3 Technology Stack

Layer	Technology	Version
Frontend	[e.g., React, Blazor]	[version]
Backend API	[e.g., ASP.NET Core, Express]	[version]
Database	[e.g., PostgreSQL, SQL Server]	[version]
Cache	[e.g., Redis]	[version]
Message Broker	[e.g., RabbitMQ, Kafka]	[version]
Hosting	[e.g., Azure AKS, AWS ECS]	N/A

2.4 Communication Patterns

From	To	Protocol	Pattern
Web App	API Gateway	HTTPS	Synchronous
API Gateway	Auth Service	gRPC	Synchronous
API Gateway	Order Service	HTTPS/REST	Synchronous
Order Service	Notification Service	AMQP	Async (event)

3. API Specifications

3.1 API Design Principles

[REST / GraphQL / gRPC. Versioning strategy. Naming conventions.]

3.2 Authentication and Authorization

[OAuth 2.0, JWT, API keys. Token format and validation. Scope/role model.]

3.3 Endpoints

POST /api/v1/orders

Description: Create a new order Authentication: Bearer token (JWT) Authorization: Role: customer

Request:

{
  "items": [
    {
      "productId": "WM001",
      "quantity": 2
    }
  ],
  "shippingAddress": {
    "street": "123 Main St",
    "city": "Springfield",
    "state": "IL",
    "zip": "62701"
  },
  "paymentMethodId": "pm_abc123"
}

Response (201 Created):

{
  "orderId": "ord_789xyz",
  "status": "pending",
  "total": 59.98,
  "currency": "USD",
  "estimatedDelivery": "2025-02-15",
  "createdAt": "2025-02-08T14:30:00Z"
}

Error Responses:

Status	Code	Description
400	INVALID_REQUEST	Missing or malformed fields
401	UNAUTHORIZED	Invalid or expired token
403	FORBIDDEN	Insufficient permissions
409	OUT_OF_STOCK	Requested quantity unavailable
422	VALIDATION_ERROR	Business rule violation
500	INTERNAL_ERROR	Unexpected server error

3.4 Rate Limiting

[Requests per minute per user/IP. Rate limit headers. Retry-After behavior.]

3.5 Pagination

[Cursor-based / offset-based. Page size limits. Response envelope format.]

4. Data Models

4.1 Entity-Relationship Diagram

erDiagram
    User ||--o{ Order : places
    Order ||--|{ OrderItem : contains
    OrderItem }o--|| Product : references
    Order ||--o| Payment : "paid by"
    User ||--o{ Address : has

4.2 Schema Definitions

Users Table

Column	Type	Constraints	Description
id	UUID	PK	Unique identifier
email	VARCHAR(255)	UNIQUE, NOT NULL	Login email
password_hash	VARCHAR(255)	NOT NULL	Bcrypt hash
created_at	TIMESTAMPTZ	NOT NULL, DEFAULT NOW	Account creation time
updated_at	TIMESTAMPTZ	NOT NULL	Last modification

Orders Table

Column	Type	Constraints	Description
id	UUID	PK	Unique identifier
user_id	UUID	FK -> Users(id)	Customer reference
status	VARCHAR(50)	NOT NULL	Order status enum
total	DECIMAL(10,2)	NOT NULL	Order total amount
currency	CHAR(3)	NOT NULL, DEFAULT 'USD'	ISO 4217 currency
created_at	TIMESTAMPTZ	NOT NULL, DEFAULT NOW	Order creation time

4.3 Data Migration Strategy

[How schema changes are applied. Tool (e.g., Flyway, EF Migrations). Backward compatibility during rolling deployments.]

4.4 Data Retention and Archival

[Retention policies. PII handling. Archival strategy for historical data.]

5. Security Requirements

5.1 Authentication

[Mechanism: OAuth 2.0 + PKCE, JWT tokens, session management. Token lifetime and refresh strategy.]

5.2 Authorization

[RBAC / ABAC model. Role definitions. Permission matrix.]

Role	Create Order	View Orders	Cancel Order	Admin Panel
Customer	Yes	Own only	Own (pending)	No
Support	No	All	All	No
Admin	Yes	All	All	Yes

5.3 Data Protection

[Encryption at rest (AES-256). Encryption in transit (TLS 1.2+). PII handling. GDPR/CCPA compliance measures.]

5.4 Input Validation

[Validation strategy. Sanitization. SQL injection prevention. XSS prevention. CSRF protection.]

5.5 Secrets Management

[Vault / Key Vault / SSM. Secret rotation policy. No secrets in code or environment files.]

5.6 Audit Logging

[What is logged. Log retention. Tamper-proof storage.]

6. Performance Requirements

6.1 Latency Targets

Operation	P50 Target	P95 Target	P99 Target
API response	< 100ms	< 300ms	< 1s
Page load (FCP)	< 1.5s	< 3s	< 5s
Search results	< 200ms	< 500ms	< 2s
Order placement	< 500ms	< 1s	< 3s

6.2 Throughput

[Expected RPS. Peak load projections. Burst capacity.]

6.3 Availability

[SLA target (e.g., 99.9%). Planned maintenance windows. Failover strategy. RTO and RPO.]

6.4 Scalability

[Horizontal vs vertical scaling strategy. Auto-scaling triggers and limits. Database read replicas / sharding plan.]

6.5 Caching Strategy

[Cache layers (CDN, application cache, database cache). Cache invalidation strategy. TTL policies.]

7. Dependencies

7.1 External Services

Service	Purpose	SLA	Fallback Strategy
[Payment Provider]	Payment processing	99.95%	Queue and retry
[Email Provider]	Transactional email	99.9%	Fallback provider
[CDN Provider]	Static asset delivery	99.99%	Origin fallback

7.2 Internal Dependencies

[Other team services, shared libraries, platform services.]

7.3 Third-Party Libraries

[Key libraries with versions. License compliance. Update strategy.]

8. Technical Constraints

• [Constraint 1: e.g., Must run on .NET 8 LTS]
• [Constraint 2: e.g., Must use PostgreSQL (organizational standard)]
• [Constraint 3: e.g., Must support IE 11 (legacy customer requirement)]
• [Constraint 4: e.g., Must integrate with existing SSO via SAML 2.0]
• [Constraint 5: e.g., Maximum deployment artifact size 500MB]

9. Deployment Plan

9.1 Environments

Environment	Purpose	URL
Development	Active development	dev.example.internal
Staging	Pre-production testing	staging.example.internal
Production	Live traffic	api.example.com

9.2 CI/CD Pipeline

[Build → Test → Security Scan → Deploy → Smoke Test → Rollout] [Tool: GitHub Actions / Azure DevOps / Jenkins]

9.3 Rollout Strategy

[Blue-green / Canary / Rolling update. Canary percentage and promotion criteria. Feature flags for gradual rollout.]

9.4 Rollback Plan

[Automated rollback triggers (error rate, latency). Manual rollback procedure. Database rollback strategy (backward-compatible migrations).]

9.5 Monitoring and Alerting

[Metrics: latency, error rate, CPU, memory, queue depth. Tools: Prometheus, Grafana, Datadog, Azure Monitor. Alert thresholds and escalation policy.]

10. Open Technical Questions

• [Question 1 -- owner, target date]
• [Question 2 -- owner, target date]
• [Question 3 -- owner, target date]

Appendix

A. Glossary

[Domain-specific technical terms and acronyms.]

B. Related Documents

• PRD: [link]
• ADRs: [links to relevant architecture decisions]
• API Schema: [link to OpenAPI/Swagger spec]
• Runbook: [link to operational runbook]

## TRD Example: Order Service

```markdown
# TRD: Order Service

| Field            | Value                     |
|------------------|---------------------------|
| Author           | Jane Engineer             |
| Status           | In Review                 |
| Created          | 2025-01-15                |
| PRD Reference    | PRD-042: Checkout Redesign|

## 1. System Overview

The Order Service manages the complete order lifecycle from creation
through fulfillment. It replaces the order module in the monolith
as part of the microservices migration (see ADR-007).

## 2. Architecture

Architecture style: Event-driven microservice (see ADR-012).

The service exposes a REST API for synchronous order operations
and publishes domain events to RabbitMQ for downstream consumers
(notification, analytics, fulfillment).

## 3. Key API Endpoints

- POST /api/v1/orders -- Create order
- GET /api/v1/orders/{id} -- Get order by ID
- GET /api/v1/orders?userId={id} -- List user orders
- PATCH /api/v1/orders/{id}/cancel -- Cancel order
- POST /api/v1/orders/{id}/refund -- Initiate refund

## 4. Data Model

Orders table with OrderItems join table. Uses PostgreSQL with
EF Core migrations. See schema definitions in Section 4.2 above.

## 5. Events Published

| Event              | Trigger               | Consumers                  |
|--------------------|-----------------------|----------------------------|
| OrderCreated       | New order placed      | Notification, Analytics    |
| OrderCancelled     | Order cancelled       | Notification, Fulfillment  |
| OrderFulfilled     | Order shipped         | Notification, Analytics    |
| PaymentProcessed   | Payment confirmed     | Order (self), Analytics    |

Relationship to Other Documents

BRD (Business Requirements)
 |  Business case and justification
 v
PRD (Product Requirements)
 |  What to build, user stories, success metrics
 v
TRD (Technical Requirements)  <-- YOU ARE HERE
 |  How to build it -- architecture, APIs, data, deployment
 |
 +---> ADR (Architecture Decision Records)
 |     Individual decisions made during TRD creation
 |     (e.g., "Why PostgreSQL over MongoDB?")
 |
 +---> RFC (Request for Comments)
 |     Proposals for significant technical changes
 |     that need team-wide input before finalizing
 |
 v
Implementation
 |  Code guided by the TRD
 v
Gherkin / Gauge (Executable Specs)
    Verification that implementation meets requirements

Best Practices

• Reference the PRD -- every technical decision should trace back to a product requirement. If a TRD section cannot be justified by the PRD, question whether it belongs.
• Include diagrams -- architecture diagrams (C4, sequence, ERD) communicate structure far better than prose alone. Use Mermaid for Markdown-native rendering.
• Specify API contracts precisely -- include request/response schemas, error codes, authentication, pagination, and rate limiting. Consider providing an OpenAPI spec as an appendix.
• Define performance targets with percentiles -- P50, P95, and P99 targets are more useful than averages, which hide tail latency.
• Document the security model explicitly -- authentication, authorization, encryption, input validation, and secrets management deserve dedicated sections, not afterthoughts.
• Plan for failure -- include rollback procedures, circuit breaker strategies, fallback behaviors, and disaster recovery in the deployment plan.
• Record decisions as ADRs -- when the TRD makes a significant technical choice (database, framework, architecture style), create a linked ADR to capture the context and trade-offs.
• Keep it current -- update the TRD as the system evolves. An outdated TRD is a liability, not an asset.
• Review with the full engineering team -- the TRD should be reviewed by backend, frontend, infrastructure, security, and QA engineers before implementation begins.
• Use version control -- store the TRD in the repository alongside the code it describes so it evolves with the system.