A technical requirements document for a Series A cloud-based product must balance specificity with flexibility — specific enough that engineering can build without daily PM clarification, flexible enough that implementation details can evolve as the team learns — and it should be written in the language of user behaviors and system contracts, not implementation choices.
Series A startups write TRDs for the first time at exactly the wrong moment: when they're moving fast and under pressure to ship. The result is either a document too vague to use ("the system should be scalable") or too prescriptive ("use Redis for caching with a 300ms TTL"). This template shows the right level of specificity for each section.
TRD Structure for a Cloud-Based Series A Product
Section 1: Product Context
Purpose: One paragraph. Why does this product exist and what problem does it solve for which user?
Scope: What is included in this TRD and what is explicitly out of scope?
Success definition: What measurable outcomes indicate this product is working?
Section 2: Functional Requirements
Write each functional requirement in the format:
FR-[number]: [Actor] can [action] so that [outcome]. Acceptance criteria: [Specific, testable condition that proves the requirement is met]
Example:
FR-001: A registered user can upload a CSV file up to 50MB so that their data is available for analysis within 30 seconds. Acceptance criteria: File upload completes in under 5 seconds for a 50MB file; processing completes in under 30 seconds; user receives a success notification with row count.
Section 3: Non-Functional Requirements
H3: Performance
- API response time: p95 under 200ms for read operations, p95 under 500ms for write operations
- Throughput: System must handle N concurrent users at peak (define N based on growth projections)
- Availability: 99.9% uptime SLA (43.8 minutes downtime per month maximum)
H3: Scalability
- Horizontal scaling: System must scale horizontally without architectural changes to support 10x current load
- Database growth: Data model must support N million records without query degradation (define N at 3x projected 12-month volume)
H3: Security
- Authentication: OAuth 2.0 / OpenID Connect required
- Authorization: Role-based access control (RBAC) with principle of least privilege
- Data encryption: At rest (AES-256) and in transit (TLS 1.3)
- Secrets management: AWS Secrets Manager / HashiCorp Vault — no hardcoded credentials
H3: Compliance
- GDPR: Right to erasure and data portability required for EU users
- SOC 2 Type II: System must be instrumented for SOC 2 audit from day one
- Data residency: [Specify if customer data must remain in specific regions]
Section 4: API Contracts
For each external-facing API endpoint:
- Endpoint path and HTTP method
- Authentication requirements
- Request schema with required vs. optional fields
- Response schema with status codes
- Rate limiting rules
- Versioning strategy
Section 5: Infrastructure Architecture
Diagram or describe:
- Cloud provider(s) and regions
- Primary services (compute, database, cache, storage, queue)
- Network topology (VPC, subnets, security groups)
- Deployment model (containers, serverless, VMs)
- Observability stack (logging, metrics, tracing)
Section 6: Open Questions
List all decisions not yet made with an owner and target resolution date. An unresolved open question in a TRD is better than a wrong assumption baked into a requirement.
FAQ
Q: What is a technical requirements document for a cloud-based product? A: A document that specifies functional requirements (what the system does), non-functional requirements (how well it performs), API contracts, infrastructure architecture, and compliance requirements at a level of specificity that allows engineering to build without daily PM clarification.
Q: What level of detail should a Series A TRD include? A: Functional requirements at the behavior level, performance requirements as measurable targets, API contracts with schemas, and infrastructure at the service level — not implementation details like specific library choices or internal data structures.
Q: How do you write functional requirements for a TRD? A: Use the format Actor can action so that outcome, with specific testable acceptance criteria for each requirement.
Q: What security requirements should a Series A cloud product TRD include? A: OAuth 2.0 authentication, RBAC authorization, AES-256 encryption at rest, TLS 1.3 in transit, secrets management via a vault solution, and SOC 2 Type II instrumentation from day one.
Q: How do you handle open questions in a technical requirements document? A: List them explicitly in an Open Questions section with an owner and resolution date — an unresolved open question is better than a wrong assumption embedded in a requirement.
HowTo: Write a Technical Requirements Document for a Series A Cloud Product
- Write the Product Context section first — one paragraph on the problem, explicit scope boundaries, and measurable success definition
- Write each functional requirement in Actor/action/outcome format with specific testable acceptance criteria
- Define non-functional requirements as measurable targets for performance, scalability, availability, and security
- Write API contracts with request and response schemas, authentication requirements, and rate limiting rules for each external endpoint
- Diagram the infrastructure architecture at the service level without prescribing implementation details
- List all open questions with owners and resolution dates rather than embedding assumptions in requirements