The beginning of a complex project can be the most daunting part of the entire process. There are countless tasks to complete, situations to account for, and problems to solve.
It can feel like a lot.
Your instinct is probably to jump right into it. But the best thing to do is to take a step back and create a technical design doc.
Creating a technical design document is crucial for outlining the architecture and details of a project. Whether you’re developing software, implementing a new system, or planning a complex technical solution, a solid design doc helps you account for all project aspects and provides a roadmap for your team. It helps ensure everyone is on the same page and reduces miscommunication.
So today we’re diving into everything you need to know when writing a technical design doc.
Things to know before you start
Context is key. It’s the whole reason you’re creating a technical design doc in the first place: to really dig into the project.
A technical design document outlines how a software system or feature will be implemented. It includes key details about architecture, components, data flow, and the technology stack. Unlike a functional spec (which focuses on what the system will do), a TDD focuses on how the system will achieve its goals.
This is the time to give as much context in each area as possible. Don’t shy away from pointing out different edge cases or tagging specific team members to add in their POV and elaborate on places you might have missed.
That said, include all key stakeholders and teammates who will be part of the project. Sync with another experienced engineer to act as a sounding board. Anything to help ensure that no area within the project will be missed and that your technical design doc will truly be effective. Use a collaborative document editor (like HackMD) that your entire team has access to. Open collaboration is key.
If you get it right from the start, a well-written TDD…
- Provides clarity on project goals
- Ensures all stakeholders understand the technical solution
- Minimizes scope creep by outlining a clear path forward
- Helps teams plan work effectively
- Serves as a reference throughout development
Because of that, this doc should be created before project work has begun and after the team has decided to take on the project.
Be sure to give yourself a week or two to flesh out all angles of the project. You don’t want to rush through this. You want to ensure everyone has had time to feed into it, review it, and discuss it before work begins.
What goes into a technical design doc?
The sections below dive into the different areas of a technical design doc. To start, list the project leader, as well as any other related links, like Linear or Airtable boards.
Purpose
Start by explaining the purpose of the document. What problem is this technical solution solving? This should be the north star for your project.
Background
Here we’re diving into context around why the problem is important, how it was brought to light, how it affects users, any past efforts to solve this problem, who the key stakeholders are, how this project fits into the overall strategy or roadmap, and anything else to ground the project. You’re taking this project on for a reason. Dig into that here.
Goals
Next, think about how you’ll measure the success of the project. What should the end result look like? List here the product or technical requirements and business goals to be reached.
You can also use this section to acknowledge the out-of-scope or future goals. So that your readers know you’ve considered them, but they’re not within the scope of this project.
Assumptions
Describe the conditions and resources needed for the project or solution to work as intended. Will you ask for a budget or additional teams to support the project?
Detailed design
This is the bulk of your technical design doc. It requires the most research, planning, and prep work. Here is where you dive into solving the technical problem. Use pseudocode, diagrams, sample API requests/responses, and flow charts – whatever you need to illustrate your solution.
At a high level, you should include…
- A description of the architecture: The core system components (like servers, databases, and APIs), the data flow between components, and external dependencies (like third-party services).
- The data model: The database schemas, object models, or data structures used in the system.
- A workflow outline: How the system will work from end to end. Provide a step-by-step walkthrough of the key workflows or processes. This is where you can highlight key decision points, such as handling errors or scaling processes.
- The ideal tech stack: The technologies used to build the system or project (like programming languages, frameworks, libraries, and tools).
If applicable, this is where you should discuss the trade-offs between this solution and the current solution or an alternative. And do you need a migration strategy? Describe that strategy and the process to migrate successfully
Visual diagrams (using tools like HackMD) can be helpful in this section.
Impact
Now that you’ve described the design in detail, dive into the project’s impact. How will it affect the overall performance of the product, the security, or other aspects of your system?
Risks
Are there potential risks to keep in mind? Don’t be afraid to add those, too. It means you’ve thought through all possible angles and ensures you’re prepared should a fire happen in the actual build. You can even take it a step further by creating a monitoring / alerting plan.
Implementation plan
To keep your project on track, include a high-level timeline with key milestones and deliverables. You will likely refine this as you go, but having a rough plan helps stakeholders understand when they can expect results.
And is there a project management tool you’re using to track progress? It should be linked at the top of your document, but here is where you describe how that tool will be used throughout the build.
Tests
With the design system accounted for and the risks highlighted, now is the time to explain how testing will be implemented. What tests will you write? How will you ensure everything is working correctly, requirements have been met, and all risks are accounted for before you go live?
Release plan
Last, but certainly not least, how will you launch your project? What do the deployment architecture and environments look like? Is there a phased roll-out plan? And how will you communicate internally (and externally) throughout that process?
After your doc is written
Take a second to review your document. Double-check it encompasses all angles of the project and all feedback from important stakeholders. Make sure the doc is clear enough that anyone new could hit the ground running without syncing with you.
Once that’s complete, now is the time to review with the team and get to work!
Ultimately, the technical design doc should function as a resource while you build your project. Be sure to keep this doc updated as you progress throughout the build and systems evolve. You don’t want to reference outdated information.
Collaboration is key
A well-crafted technical design document is so much more than a document; it’s a vital tool for aligning teams, anticipating challenges, and executing projects efficiently. And as mentioned throughout, it’s a team effort. The best TDD’s come from open collaboration.
With HackMD’s markdown editor, you and your team can work together in real-time, sharing feedback, editing drafts, and brainstorming ideas all in one place. HackMD’s collaborative environment ensures everyone’s voice is heard, and important insights aren’t missed.
This continuous, open collaboration is key to the success of the TDD — and ultimately, the entire project. When teams work together, they not only avoid potential pitfalls but also build a stronger, more well-rounded solution from the start.
Sign up or create a note today to begin your technical design doc!
