Meet the Author
Background
Daniel spent the first seven years of his career as a backend engineer at B2B SaaS companies, building the kind of systems where a missing field in a spec could mean an overcharged customer, a failed payment retry, or a deployment that could not be safely rolled back.
In 2019 he moved into a tech lead role, responsible for engineering handoffs, spec review gates, and QA alignment across teams of 8–15 engineers. That experience — watching well-intentioned teams ship rework because the requirement document left too much to interpretation — is the direct origin of everything published on this site.
Daniel started Spec Coding in November 2025 to give teams a practical reference that covers the full delivery lifecycle: from writing the first draft of a spec, to defining acceptance criteria that QA can actually execute, to designing the rollback plan before code is merged.
Experience Timeline
Backend engineer at a mid-sized e-commerce SaaS, building on a Java/PostgreSQL stack. Worked on order management, payment retry logic, and fulfillment APIs. First exposure to production incidents caused by under-specified edge cases.
Senior engineer at a B2B CRM platform serving 2,000+ enterprise accounts. Led API contract design for a multi-tenant data model migration. Introduced OpenAPI-first workflows after a breaking change reached production undetected.
Tech lead across billing, internal tooling, and partner API teams (8 – 15 engineers). Established spec review gates, acceptance criteria standards, and pre-merge checklists that reduced rework by an estimated 40 % across two annual release cycles and cut post-release hotfixes from ~12 per quarter to fewer than 3.
Independent engineering writer and consultant. Founded Spec Coding to publish practical spec-first guides. Consults with early-stage SaaS teams on specification workflows and release engineering.
What Daniel Writes About
Every article on Spec Coding is drawn from a real delivery scenario Daniel has encountered or has been consulted on. Topics include:
- Spec-first adoption — how to introduce specification discipline to a team already mid-sprint, without disrupting velocity.
- API contracts — versioning strategies, contract testing pipelines, error taxonomy, and backward compatibility review.
- Acceptance criteria — writing Given/When/Then scenarios that QA can execute without interviewing the author.
- Risk-heavy patterns — idempotency, concurrency, rollout/rollback design, and the postmortem behind common billing incidents.
- Reusable templates — downloadable spec documents, PRD-to-spec conversion guides, and review scorecard tools.
Editorial Accountability
Daniel reviews and updates every article on Spec Coding personally. When readers report outdated or inaccurate content, he investigates and publishes corrections with updated metadata. The full publishing and correction process is documented in the Editorial Policy.
For factual corrections, feedback, or collaboration inquiries, use the contact page or email guoking678@gmail.com. Daniel responds to all editorial messages within three business days.
Selected Articles by Daniel Marsh
- What Is Spec-First Development? (Complete Guide)
- PRD vs Technical Spec: What's the Difference?
- How to Write Testable Software Specifications
- Spec-First vs Agile: Conflict or Complement?
- 10 Common Mistakes in Software Specifications
- Postmortem: Preventing a Billing Incident with Spec-First
- Versioning Strategies for API Contracts
- Contract Testing Plan: From OpenAPI to CI
- View all articles →
Open source projects
- spec-kit — Markdown specification templates for spec-first software development. Includes feature specs, API contracts, database migration specs, incident postmortems, and review checklists.
- openapi-spec-starter — OpenAPI starter kit with CI-integrated contract testing. Includes Spectral linting, Prism mock validation, Schemathesis fuzz testing, and a GitHub Actions workflow.
Find Daniel Online
- GitHub: GitHub — spec-first development resources
- Email: guoking678@gmail.com
- Site: spec-coding.dev