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How to Write a TRD: Technical Requirements Document Guide

A TRD, or Technical Requirements Document, specifies the technology environment a system needs to run. While a PRD defines what to build and an FRD defines how it should behave, the TRD defines the infrastructure, hardware, software, and platform requirements that the system depends on. It answers the question: what technical foundation does this system need to operate correctly?

A TRD is especially important when the system has specific hardware dependencies, must run on a particular cloud platform, needs to integrate with legacy infrastructure, or must meet compliance requirements that dictate technology choices.

Key insight

A TRD is not about what the software does (that is the FRD) or how well it performs (that is the NFR section of the SRD). A TRD specifies the technical ecosystem — the servers, networks, databases, operating systems, third-party tools, and platform services that the system requires.

Who writes it and for whom

The TRD owner is typically a Systems Architect, Infrastructure Engineer, DevOps Lead, or Technical Project Manager — someone who understands the full technology stack from hardware to application layer.

ReaderWhat they look for
DevOps / SREServer specs, cloud services, networking, monitoring tools
Backend engineersDatabase requirements, runtime versions, dependency constraints
Security teamEncryption standards, access controls, compliance requirements
ProcurementHardware specifications, licensing costs, vendor requirements
Project managersTechnology risks, dependencies, lead times for infrastructure

When you need a TRD — and when you don’t

You need a TRD when:

  • The project involves specific hardware procurement (on-premise servers, IoT devices, specialized equipment)
  • Cloud infrastructure decisions need to be documented and approved before provisioning
  • Multiple teams or vendors need to agree on a shared technology stack
  • Compliance or security requirements dictate specific technology choices (encryption standards, data residency, certified platforms)
  • You are migrating from one platform to another and need to document both current and target environments

A TRD is unnecessary when:

  • The team has full autonomy over technology decisions and infrastructure is already provisioned
  • The project runs on a standardized platform where infrastructure is a shared service
  • The PRD or SRD already covers technology constraints in enough detail
  • The project is a prototype or experiment with no infrastructure commitments

What a TRD contains

Core sections

A TRD typically includes six sections:

  1. Introduction — purpose of the document, scope of the system, relationship to other documents (PRD, SRD, architecture docs), and definitions of technical terms.

  2. Hardware Requirements — physical server specifications, networking equipment, storage systems, IoT devices, or end-user devices that the system requires.

    ComponentSpecificationQuantityPurpose
    Application server16 vCPU, 64GB RAM, 500GB SSD3Primary application tier
    Database server32 vCPU, 128GB RAM, 2TB NVMe2Primary + replica
    Load balancerF5 Big-IP or equivalent1Traffic distribution

  3. Software Requirements — operating systems, runtime environments, databases, message brokers, caching layers, and all third-party software the system depends on.

    SoftwareVersionLicensePurpose
    Ubuntu Server24.04 LTSOpen sourceOS for application servers
    PostgreSQL16.xOpen sourcePrimary database
    Redis7.xOpen sourceSession cache and rate limiting
    Node.js22 LTSOpen sourceApplication runtime
    Nginx1.27+Open sourceReverse proxy

  4. Platform and Infrastructure Requirements — cloud provider services, networking configuration, DNS, CDN, container orchestration, CI/CD pipeline requirements, and environment specifications (development, staging, production).

    For cloud deployments:

    ServiceProviderConfigurationPurpose
    ComputeAWS EC2 / GCP GCEc6i.4xlarge or equivalentApplication servers
    DatabaseAWS RDS / GCP Cloud SQLMulti-AZ, automated backupsManaged PostgreSQL
    Object storageS3 / GCSStandard tier, versioning enabledFile uploads, backups
    CDNCloudFront / CloudflareGlobal edge cachingStatic asset delivery

  5. Security and Compliance Requirements — encryption standards (at rest, in transit), authentication and authorization infrastructure, network segmentation, vulnerability scanning tools, compliance frameworks (SOC 2, HIPAA, GDPR, PCI-DSS) and their technology implications.

  6. Appendices — network diagrams, environment architecture diagrams, vendor comparison matrices, capacity planning calculations, glossary, and change log.

Key insight

The TRD should specify requirements, not implementation details. “The system requires a relational database with ACID compliance, point-in-time recovery, and read replicas” is a requirement. “Use PostgreSQL 16 on AWS RDS” is an implementation decision that may appear in the TRD when the technology choice has been made and approved.

TRD and other requirement documents

The TRD operates alongside the SRD rather than in sequence:

MRD → BRD → PRD → FRD → SRD
                           ↑
                          TRD (infrastructure layer)
DocumentDefinesExample
SRDWhat the software does and how well”System responds in 200ms at P95”
TRDWhat infrastructure supports it”Requires 3 app servers with 16 vCPU each behind a load balancer”
FRDHow the system behaves”User clicks reset → receives email within 60s”

The SRD says “the system shall support 10,000 concurrent users.” The TRD says “to support 10,000 concurrent users, the system requires three c6i.4xlarge instances with auto-scaling configured to add capacity at 70% CPU.”

Common mistakes

1. Mixing functional requirements with technical requirements. “The system shall allow users to upload files up to 100MB” is a functional requirement (FRD). “The system requires S3-compatible object storage with a 100MB upload limit configured at the reverse proxy” is a technical requirement (TRD).

2. Specifying technology without justification. “Use Kafka” is not a requirement. “The system requires a distributed message broker with at-least-once delivery, message replay capability, and throughput of 50,000 messages/second” is a requirement. Whether that translates to Kafka, Pulsar, or Redpanda is an implementation decision.

3. Ignoring environment parity. The TRD should specify requirements for all environments — development, staging, and production. If developers run the system on a single Docker container but production requires a Kubernetes cluster with 12 nodes, the TRD documents both.

4. No capacity planning. A TRD without capacity projections becomes obsolete the moment traffic grows. Include expected load at launch, projected growth (6 months, 12 months), and the infrastructure changes needed at each stage.

5. Forgetting licensing. Commercial software licenses, SaaS subscriptions, and cloud service costs belong in the TRD. Discovering that the database engine requires a $50,000/year enterprise license after architecture is finalized is a preventable problem.

Resources