Product 101: Avoid the "Thud" PRD Trap
What PMs should do instead
One of the most memorable concepts I picked up during my architecture days was the dreaded "Thud" documents. Hundreds of pages of design specs that would make a literal thud when printed and dropped on a table. The sound is symbolic of slow, heavy, expensive, and out-of-date systems the moment they land. Building the future legacy.
Product has its version of this, the "Thud" PRD.
If you’ve been a party to one or on the receiving end, you know the pain. A product requirements document that tries to capture the entire system end-to-end including every workflow, rule, state change, interaction, and edge case. The goal is completeness, but the result is churn and friction.
You can’t ship a Thud PRD in a sprint. You can’t ship it in a quarter. Most of the time, you can’t ship it at all because it changes as soon as it lands.
PRDs should be scoped to a single epic
Measurable outcomes must be defined
Instrumentation must be a first-class citizen
A/B testing should be foundational, not an afterthought
Why “Thud” PRDs Fail
The features are all spec’d out and passed the review. Precious design and engineering cycles are consumed. Then the team is lost in the wilderness building who knows what. The problem is not lack of execution. It is that we planned for the wrong things.
The Thud PRD is built on a false belief: that if we just plan enough, we’ll get it right. The reality is you have no clue what you need to build three months from now.
You are guessing until users interact with the product
Most assumptions will be outdated before delivery
Big specs get political, not better
Over-scoping creates pressure to deliver features users didn’t ask for
The result is delay, rework, churn, and wasted effort.
A Real-World Example
As a product owner at a financial services company in the mid 2000s, I developed a 52-page PRD for a risk and compliance management platform. It described every feature, system behavior, role, and report across the entire product. Four months in, the team shipped the beta and adoption was in the toilet. The system was technically built to spec, but completely misaligned with real workflows. The team successfully executed a death march.
I salvaged what I could. This time, I wrote a single, concise PRD, focused on a specific user problem: Risk managers wasting hours reconciling POs. There were other problems, but I put those in the backlog for future reference. Maybe we’d build them, maybe we wouldn’t.
The PRD was less than 8 pages. It included a hypothesis, metrics, personas, user stories, and acceptance criteria specific to solving that problem. Within six weeks, we had a prototype that users could test, give feedback on, and we could learn from. The result: a product that shipped on time, with 90% of features actively used in the first month, and happy customers.
The Essentials of a PRD
Avoiding the Thud doesn’t mean writing less. It means focusing on the essentials. Writing for clarity, alignment, measurement, and a specific user with a specific problem. execution. Below are the essential components:
1. Define the Problem
State the specific problem you're solving. Not a feature, not a stakeholder request. A problem backed by data.
“Developers need to configure IAM roles manually for each microservice deployment, resulting in an average of 6 hours per week in setup errors and support tickets.”
2. Identify the User Persona
Name the actual person experiencing the problem. Be concrete.
“Sarah is a backend developer managing five microservices across staging and production. She frequently provisions new environments and spends significant time troubleshooting permission issues during deployment.”
3. Form a Hypothesis
Define your solution as a testable hypothesis, tied to a measurable outcome.
“Introducing a pre-configured IAM role template library will reduce permission setup time by 80% and decrease support tickets related to misconfigurations by 50% within 60 days.”
4. Define Metrics and Success Criteria
Attach the solution to a quantifiable goal. If you can’t measure it, don’t build it.
“Reduce average IAM setup time from 90 minutes to under 15 minutes. Lower access-related support tickets from 40 to 20 per month.”
5. List Considered Options
Show what other paths were explored and why they were rejected. This reduces re-litigation later.
“We considered auto-generating policies based on historical service behavior, but the risk of over-permissioning was too high. Template-based provisioning with explicit scopes provided stronger security guardrails.”
6. Outline Instrumentation Requirements
Define what needs to be tracked to measure outcomes. Include logging, event data, dashboards, and control groups.
“Log IAM template usage by environment, track time from selection to deployment, capture permission denial events post-deployment, and segment error rates by template.”
7. Scope to an Epic or Less
Your PRD should be deliverable in a handful of sprints. If it’s larger than an epic, break it up.
“Goal: Ship within 4 sprints with . Ship initial IAM template library with five use cases (EC2, Lambda, S3, DynamoDB, SQS), including developer documentation and CLI support within three sprints with weekly milestone check-ins and demo-ready builds”
8. Include User Stories, Rules, and Test Cases
Add only the details needed to validate the problem and prove the solution. Include user stories with clear acceptance criteria that reflect the desired outcome. Describe edge cases that are relevant to the target developer persona, especially those that could cause failure in real-world environments. Document any business rules or compliance constraints that must be enforced during implementation. Finally, define test cases that are directly tied to the original hypothesis, ensuring that success or failure can be measured objectively.
Example stories:
“As a developer, I want to select a predefined IAM role for my Lambda function so I can deploy without writing a custom policy.”
“As a team lead, I want to restrict template usage to approved roles only.”
Acceptance criteria:
Templates apply correct least-privilege policies.
Deployment succeeds without manual policy editing.
Audit logs show role usage and associated actions.
Avoid describing the entire system. Use a separate product vision and strategy doc for that. Focus on what matters to ease your customer’s pain.
Good vs. Bad: PRD Comparison
Don’t Mistake Agile for Adaptability
Agile rituals won’t save a bad PRD. You can iterate on the wrong thing indefinitely. Without clearly defined problems, measurable outcomes, feedback loops, and learning mechanisms, Agile becomes a delivery treadmill.
Iteration only works when it’s grounded in data and structured for learning.
Final Takeaway
If your PRD can’t be shipped within a few sprints, it’s too big. If it doesn’t define a specific user problem, it’s too vague. If it lacks metrics, it’s just a guess. To simplify it, if your PRD is bigger than an epic, then trim it down.
Kill the “Thud” PRD. Build requirements that help teams learn, adapt, and deliver impact.
Start with the customer problem, form a hypothesis, define the customer’s end state, and work backwards from that.
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