A practical guide to writing technical specs
As a software engineer, your primary role is to solve technical problems. Your first impulse may be to immediately jump straight into writing code. But that can be a terrible idea if you haven’t thought through your solution.
You can think through difficult technical problems by writing a technical spec. Writing one can be frustrating if you feel like you’re not a good writer. You may even think that it’s an unnecessary chore. But writing a technical spec increases the chances of having a successful project, service, or feature that all stakeholders involved are satisfied with. It decreases the chances of something going horribly wrong during implementation and even after you’ve launched your product.
In this article, I’ll walk you through how to write a technical spec that ensures a strong product.
What is a technical specification document?
A technical specification document outlines how you’re going to address a technical problem by designing and building a solution for it. It’s sometimes also referred to as a technical design document, a software design document, or an engineering design document. It’s often written by the engineer who will build the solution or be the point person during implementation, but for larger projects, it can be written by technical leads, project leads, or senior engineers. These documents show the engineer’s team and other stakeholders what the design, work involved, impact, and timeline of a feature, project, program, or service will be.
Why is writing a technical spec important?
Technical specs have immense benefits to everyone involved in a project: the engineers who write them, the teams that use them, even the projects that are designed off of them. Here are some reasons why you should write one.
Benefits to engineers
By writing a technical spec, engineers are forced to examine a problem before going straight into code, where they may overlook some aspect of the solution. When you break down, organize, and time box all the work you’ll have to do during the implementation, you get a better view of the scope of the solution. Technical specs, because they are a thorough view of the proposed solution, they also serve as documentation for the project, both for the implementation phase and after, to communicate your accomplishments on the project.
With this well-thought out solution, your technical spec saves you from repeatedly explaining your design to multiple teammates and stakeholders. But nobody’s perfect; your peers and more seasoned engineers may show you new things from them about design, new technologies, engineering practices, alternative solutions, etc. that you may not have come across or thought of before. They may catch exceptional cases of the solution that you may have neglected, reducing your liability. The more eyes you have on your spec, the better.
Benefits to a team
A technical spec is a straightforward and efficient way to communicate project design ideas between a team and other stakeholders. The whole team can collaboratively solve a problem and create a solution. As more teammates and stakeholders contribute to a spec, it makes them more invested in the project and encourages them to take ownership and responsibility for it. With everyone on the same page, it limits complications that may arise from overlapping work. Newer teammates unfamiliar with the project can onboard themselves and contribute to the implementation earlier.
Benefits to a project
Investing in a technical spec ultimately results in a superior product. Since the team is aligned and in agreement on what needs to be done through the spec, big projects can progress faster. A spec is essential in managing complexity and preventing scope and feature creep by setting project limits. It sets priorities thereby making sure that only the most impactful and urgent parts of a project go out first.
Post implementation, it helps resolve problems that cropped up within the project, as well as provide insight in retrospectives and postmortems. The best planned specs serve as a great guide for measuring success and return on investment of engineering time.
What to do before writing a technical spec
Gather the existing information in the problem domain before getting started. Read over any product/feature requirements that the product team has produced, as well as technical requirements/standards associated with the project. With this knowledge of the problem history, try to state the problem in detail and brainstorm all kinds of solutions you may think might resolve it. Pick the most reasonable solution out of all the options you have come up with.
Remember that you aren’t alone in this task. Ask an experienced engineer who’s knowledgeable on the problem to be your sounding board. Invite them to a meeting and explain the problem and the solution you picked. Lay out your ideas and thought process and try to persuade them that your solution is the most appropriate. Gather their feedback and ask them to be a reviewer for your technical spec.
Finally, it’s time to actually write the spec. Block off time in your calendar to write the first draft of the technical spec. Usea collaborative document editor that your whole team has access to. Get a technical spec template (see below) and write a rough draft.
Contents of a technical spec
There are a wide range of problems being solved by a vast number of companies today. Each organization is distinct and creates its own unique engineering culture. As a result, technical specs may not be standard even within companies, divisions, teams, and even among engineers on the same team. Every solution has different needs and you should tailor your technical spec based on the project. You do not need to include all the sections mentioned below. Select the sections that work for your design and forego the rest.
From my experience, there are seven essential parts of a technical spec: front matter, introduction, solutions, further considerations, success evaluation, work, deliberation, and end matter.
1. Front matter
- Created on
- Last updated
- Epic, ticket, issue, or task tracker reference link
a. Overview, Problem Description, Summary, or Abstract
- Summary of the problem (from the perspective of the user), the context, suggested solution, and the stakeholders.
b. Glossary or Terminology
- New terms you come across as you research your design or terms you may suspect your readers/stakeholders not to know.
c. Context or Background
- Reasons why the problem is worth solving
- Origin of the problem
- How the problem affects users and company goals
- Past efforts made to solve the solution and why they were not effective
- How the product relates to team goals, OKRs
- How the solution fits into the overall product roadmap and strategy
- How the solution fits into the technical strategy
d. Goals or Product and Technical Requirements
- Product requirements in the form of user stories
- Technical requirements
e. Non-Goals or Out of Scope
- Product and technical requirements that will be disregarded
f. Future Goals
- Product and technical requirements slated for a future time
- Conditions and resources that need to be present and accessible for the solution to work as described.
a. Current or Existing Solution / Design
- Current solution description
- Pros and cons of the current solution
b. Suggested or Proposed Solution / Design
- External components that the solution will interact with and that it will alter
- Dependencies of the current solution
- Pros and cons of the proposed solution
- Data Model / Schema Changes
- Schema definitions
- New data models
- Modified data models
- Data validation methods
- Business Logic
- API changes
- Error states
- Failure scenarios
- Conditions that lead to errors and failures
- Presentation Layer
- User requirements
- UX changes
- UI changes
- Wireframes with descriptions
- Links to UI/UX designer’s work
- Mobile concerns
- Web concerns
- UI states
- Error handling
- Other questions to answer
- How will the solution scale?
- What are the limitations of the solution?
- How will it recover in the event of a failure?
- How will it cope with future requirements?
c. Test Plan
- Explanations of how the tests will make sure user requirements are met
- Unit tests
- Integrations tests
d. Monitoring and Alerting Plan
- Logging plan and tools
- Monitoring plan and tools
- Metrics to be used to measure health
- How to ensure observability
- Alerting plan and tools
e. Release / Roll-out and Deployment Plan
- Deployment architecture
- Deployment environments
- Phased roll-out plan e.g. using feature flags
- Plan outlining how to communicate changes to the users, for example, with release notes
f. Rollback Plan
- Detailed and specific liabilities
- Plan to reduce liabilities
- Plan describing how to prevent other components, services, and systems from being affected
g. Alternate Solutions / Designs
- Short summary statement for each alternative solution
- Pros and cons for each alternative
- Reasons why each solution couldn’t work
- Ways in which alternatives were inferior to the proposed solution
- Migration plan to next best alternative in case the proposed solution falls through
4. Further Considerations
a. Impact on other teams
- How will this increase the work of other people?
b. Third-party services and platforms considerations
- Is it really worth it compared to building the service in-house?
- What are some of the security and privacy concerns associated with the services/platforms?
- How much will it cost?
- How will it scale?
- What possible future issues are anticipated?
c. Cost analysis
- What is the cost to run the solution per day?
- What does it cost to roll it out?
d. Security considerations
- What are the potential threats?
- How will they be mitigated?
- How will the solution affect the security of other components, services, and systems?
e. Privacy considerations
- Does the solution follow local laws and legal policies on data privacy?
- How does the solution protect users’ data privacy?
- What are some of the tradeoffs between personalization and privacy in the solution?
f. Regional considerations
- What is the impact of internationalization and localization on the solution?
- What are the latency issues?
- What are the legal concerns?
- What is the state of service availability?
- How will data transfer across regions be achieved and what are the concerns here?
g. Accessibility considerations
- How accessible is the solution?
- What tools will you use to evaluate its accessibility?
h. Operational considerations
- Does this solution cause adverse aftereffects?
- How will data be recovered in case of failure?
- How will the solution recover in case of a failure?
- How will operational costs be kept low while delivering increased value to the users?
- What risks are being undertaken with this solution?
- Are there risks that once taken can’t be walked back?
- What is the cost-benefit analysis of taking these risks?
j. Support considerations
- How will the support team get across information to users about common issues they may face while interacting with the changes?
- How will we ensure that the users are satisfied with the solution and can interact with it with minimal support?
- Who is responsible for the maintenance of the solution?
- How will knowledge transfer be accomplished if the project owner is unavailable?
5. Success Evaluation
- Security impact
- Performance impact
- Cost impact
- Impact on other components and services
- List of metrics to capture
- Tools to capture and measure metrics
a. Work estimates and timelines
- List of specific, measurable, and time-bound tasks
- Resources needed to finish each task
- Time estimates for how long each task needs to be completed
- Categorization of tasks by urgency and impact
- Dated checkpoints when significant chunks of work will have been completed
- Metrics to indicate the passing of the milestone
d. Future work
- List of tasks that will be completed in the future
- Elements of the solution that members of the team do not agree on and need to be debated further to reach a consensus.
b. Open Questions
- Questions about things you do not know the answers to or are unsure that you pose to the team and stakeholders for their input. These may include aspects of the problem you don’t know how to resolve yet.
8. End Matter
a. Related Work
- Any work external to the proposed solution that is similar to it in some way and is worked on by different teams. It’s important to know this to enable knowledge sharing between such teams when faced with related problems.
- Links to documents and resources that you used when coming up with your design and wish to credit.
- Credit people who have contributed to the design that you wish to recognize.
After you’ve written your technical spec
Now that you have a spec written, it’s time to refine it. Go through your draft as if you were an independent reviewer. Ask yourself what parts of the design are unclear and you are uncertain about. Modify your draft to include these issues. Review the draft a second time as if you were tasked to implement the design just based on the technical spec alone. Make sure the spec is a clear enough implementation guideline that the team can work on if you are unavailable. If you have doubts about the solution and would like to test it out just to make sure it works, create a simple prototype to prove your concept.
When you’ve thoroughly reviewed it, send the draft out to your team and the stakeholders. Address all comments, questions, and suggestions as soon as possible. Set deadlines to do this for every issue. Schedule meetings to talk through issues that the team is divided on or is having unusually lengthy discussions about on the document. If the team fails to agree on an issue even after having in-person meetings to hash them out, make the final call on it as the buck stops with you. Request engineers on different teams to review your spec so you can get an outsider’s perspective which will enhance how it comes across to stakeholders not part of the team. Update the document with any changes in the design, schedule, work estimates, scope, etc. even during implementation.
Writing test specs can be an impactful way to guarantee that your project will be successful. A little planning and a little forethought can make the actual implementation of a project a whole lot easier.Tags: bulletin, stackoverflow, technical specs
Very nice writeup Zara 😀
Complete idea information to your blog. thanks sara..
Great article. It summarized all the reasearch I had to do months ago in a single page! It will help a lot.
That’s great, Franco. I had the same exact frustrating problem earlier. Having a template definitely helps out a bunch.
greate work, have any template more better
I am a civil engineer and you just helped a great deal. Some people cannot explain the thought process behind their good writing so it is difficult to learn from them. Thank you. Thank you. Thank you.
Who would write a technical spec, a technical product owner or a coder
Ma’am, I did not find your Twitter account. Can I translate this article, please? I am the editor of InfoQ China. I think your article, is really great and will help Chinese readers learn how to write technical specifications. My Twitter account is @liu_zhiyong and I hope to follow each other if that’s okay.
By the way, InfoQ China is a formal media organization, we strictly follow copyright requirements, and all translations we publish will include the original information.
I’m afraid our legal department does not allow translations at this time because of copyright issues. We appreciate your interest, but unfortunately, we can’t give you permission.
Well, I’m very sorry to hear that. I respect your opinion and abandon the plan to translate.
This is a great overview, gonna add it to my list of reference materials for new projects that I check to see what I forgot to do!
Thanks, Matt. I’m happy it will help with your future projects.
very usefull docuement
I’m glad it’s helpful, Ibrahim.
I would take the “software engineer” off of the first paragraph. You’ve written a guide that could be applied to writing any engineering technical specification. Very nice, clear and concise. A checklist every engineer should have in the back of his notebook.
If you’re a software engineer, I suspect that reading your code would be a very pleasant experience.
Makes sense NUFOSMATIC. A lot of what was in the template could be applied to a wide range of specs. The clarity and conciseness of the article is mostly thanks to Ryan Donovan’s thorough editing.
Great article! Well written and laid out. I already write technical documentation for the projects I work on and this will help me to have a more organized and template moving forward.
Thanks, Joshua. I’m happy you’ll get some use out of it.
I write specs but I’ve been told the “new way” is just to dive in and be “agile” and that I shouldn’t. But in my experience, planning in this way cuts down the cost of projects compared to the “agile” way by half, or better, and improves clarity and bugginess in the final UX. So I think that people are promoting specs-less development simply because they don’t know how to write them. Hopefully this article will help the dying art come back to life.
Anytime I hear someone saying we should “go agile and cut off the documentation” I get a big red flag crossing my mind. Then I enforce that we should document what is needed, whether it is a big amount of specs. Then I tell people about spec by example way of doing things, so we can have the minimum. If I have room, I broke into BDD/ ATDD way. Finally, I usually present the articles related to the Joel Test, on Joel Spolsky – co founder of Stack Overflow btw – which also says something about having specs and how to write one, despite I think BDD can be used to promote a having a spec to having a runnable spec.
I agree Star, first planning before implementing a design yields way more benefits and saves you the agony of fixing something wrong in production or the final product, especially when stakes are high.
I could not agree more!
30 years now in this business and it is only in the back half of this period that specifications seem needless to some. So I have always written myself something to follow even if no one else is going to read it. Agile seems to mean correcting mistakes. I prefer not to make too many and have a clear idea of what I am doing and why I am doing it.
My only criticism of this template is that it seems to roll a few documents into one – I am more used (or used to be) to a hierarchy of documents than one colossal one. Generally I have seen technical specs more at a Unit level whereas this seems to be all-encompassing.
Agreed somehow! Focusing upon specific module or/and writing technical spec of module of the project would be enlarged. but having such content in one place brought expert’s mind to further scrutinize and take in use as per their consensus need.
I recall developers and testers being confused when I spec’d errors for multiple rows returned off a unique index key. I said today it is indexed unique and you cannot see this, but this is not a database spec, it is a behavior spec., and it can still work if the index is dropped and data is inserted twice.
Nice write-up! I’m just a little scandalized that there’s no mention of Joel Spolsky’s classic article on this: https://www.joelonsoftware.com/2000/10/02/painless-functional-specifications-part-1-why-bother/
PS: And here are my thoughts on the difference between a technical spec and a functional spec: https://blog.beeminder.com/specs/
I don’t often read Joel Spolsky’s blog but thanks for linking his post. I will definitely check out both that and your post. Thanks for sharing.
Nice article. You’ve obviously put a lot of thought into the different aspects that should be included in technical documentation. Unfortunately, it kinda reminds me of waterfall development.
It seems like it’s trying to be the one mammoth document to describe an entire system. Maybe this approach could work for a simple system.
A more complex system’s functionality would need to be broken down into small manageable (easier to think about and to develop) chunks. I would have thought the more practical approach would be to do write a series of user stories describing from the user’s point of view what the system is expected to do and behave. From each of the user stories develop a technical document to describe how from a developer’s point-of-view how the user’s story could be technically achieved.
In a complex system, this one document would be HUGE. Not sure how easy it would be to produce and maintain. Not sure how easy it would be to read. Kinda want to break the document down so it is manageable and then it would be more likely to be used as a living, breathing piece of documentation.
Anyway, those are my initial jumbled thoughts.
You’re right about not writing a single spec for one large system, John. I wrote this from the perspective of a s/w engineer in a single team working on an already established product in a larger engineering department (with other teams working on other related products/system parts). From my experience, engineers who come on to a team build on the existing product which is planned out in quarters, sprints, etc. using task/story planning software. So in this case, engineers would be working on features or smaller products and everything is already planned out in the product requirements document and roadmap.
Great article, So much detailed expain, and helps a lot.
It is a well-written paper which helps a researcher and inventor to track his thoughts in a way even a dumb promotor understands the significance, opportunities, technical excellence, and usefulness of the proposed activity. Further, it helps one how to organize his own thoughts and actions in realizing his dreams. Many thanks for your excellent contribution.
Your completely right, J Nagabhushanam and thanks.
Zara, it would be helpful if guidelines in this article would be accompanied with links to spec examples that are written according to these guidelines.
Apologies Nik. The initial article was pretty lengthy and required some trimming to make it easier to review. So I cut out the example and some other parts to make it easier to edit.
Thanks a lot for this guideline, it is a great help.
Thanks, Denis. Happy it was helpful to you.
Do you have any examples of tools that would be great for writing a tech spec?
Google Docs and Dropbox Paper a great because your team could leave comments and collaborate on your spec.
This is absolutely good stuff!
Any comments as to have this ties to a User/Client side requirements…Any traceability consideration
Thanks, Chamesou. For user requirements, you’d translate them to user stories that you would use as your goals. I guess you could include tracing and logging in the monitoring and alerting section or just have a new section on its own. This is just a guide. If parts of what you plan on building are not touched on here, add whatever you need to it. Change this guide however you’d like to fit the needs of your product.
I left a comment on this one. Here is a way – https://medium.com/@nageshblore/the-parl-approach-or-what-is-a-microservice-e48dd951ef3e
As a Product Owner (semi-technical) this is beyond useful! Thank you
Glad you found it to be helpful Jonathan.
Very nice guide. Long time ago, I used to write specifications. I had nice templates then, but I do not have them anymore. I need to write one more. It is so nice to see good template. I will use it.
I hope this blog will be kept for long time. Still I am thinking to make copy of this template just for safe keeping :).
Thanks Alfas. You could create a Google Doc template with just the contents part to preserve it if you’d like and use it for your future specs.
Great guide. Just a nitpick: you mention there are 7 sections when in fact there are 8, and you stopped numbering them after 2 (“there are seven essential parts of a technical spec: front matter, introduction, solutions, further considerations, success evaluation, work, deliberation, and end matter”). Thanks.
Nice catch Gustavo, thanks.
This is very informative. Good technical specs can save a lot of time of all stakeholders
I would like to add that, the stake from the ‘business’ organization needs to come out strongly. See here – https://medium.com/@nageshblore/the-parl-approach-or-what-is-a-microservice-e48dd951ef3e – for a possible way to ‘bridge’ the business and technical teams.
This blog post seems to be written from the point of view of a team that has assimilated the requirements from the business organization and is then writing out a specification – for the assimilated requirements – that will be turned into a code. That code will materialize, eventually, into an artefact such as Docker image, binary, etc. The stake of the business organization should flow throughout the spec and perhaps, into the artefact also.
1. Business organization presents a vision e.g. reduce IT spend by 50% over 3 years, etc.
2. Consultant turns the vision into 2 or 3 programs that need to be executed over 2 years and support for 2 more years, etc.
3. Each program is broken down into projects e.g. db migration, refactor, sunset, cloud native, new UI, etc.
4. Every project is translated into certain deliverables e.g. NodeJs projects, database DDL, Dockerfiles, etc.
The business organization should be able to point to a project and drill down to a running artefact in production. Similarly, the developer should be able to call out the purpose of every artefact all the way upto the vision that triggered this project.
Is there any good example that demonstrates this content?
Great article! Thank you for sharing this.
I found that the heading “Further Considerations” is marked up with h2 while the other headings are with h3. Also, only the first two, “1. Front matter” and “2. Introduction” have the numbers.
Thanks for the detail-oriented read — fixed!
Wow, thank you for putting everything I was looking for in one place. I’ve spent a few hours researching this, and I really wish I would have found your summary last week.
This is great 🙂
Very well put and a comprehensive list of items mentioned. Thanks!
Thanks Zara for you wonderful input. It would great to share some sample Note.
I have written both functional and technical specs for years (SAP, PeopleSoft, Oracle, QAD) and i agree with the author that they reduce significantly the margin of errors before Go-live and specs can serve as a good way to further communicate the code story with new developers…..
Now, I prefer the unit approach and not a single bloc document….
Hey, thanks for the guide and for making it super specific like this! I think it’s important to mention that how the specs will look should also depend on who they are written for (as in, they should look different when they’re for your internal team vs. an external team.) My colleague talked about that a bit in his article on project specifications. Check it out, I think you may find it interesting: https://www.stxnext.com/blog/software-product-requirements-high-level-project-specifications-guide
In my past 20 years of development I saw a lot of technical specs. Although it is important to have all those different sections filled in, they are just metadata. The most important thing is to write a good text that explains what is actually happening. And this is about story telling. You need to explain how the things work in a thread that can be easily followed by the reader. In german we call this “Roter Faden” (red thread) and this the most important thing for people to understand what the concept is about. The better this is written, the better other people can get the idea. Then we have all those meta-data to back up the main text. No one is reading hundreds of sections especially in these days and jumping between headings is confusing. The best concepts I have ever seen have been short and I just had to read them once. They were captivating like a book.
Indeed, writing technical documentation is a separate kind of art. The article is well-structured and really informative! BTW, I’ve read another cool piece on this subject, here it is in case anyone’s interested to expand their knowledge: https://faun.pub/the-values-of-technical-documentation-443ea1b846ee.
Excellent article. Quite exhaustive. How much research has gone in to it Kudos to you Zara for bringing out such a useful article that can be used by everyone regardless of the the role or position.