Most of us have lived through this story.
The project “goes live” with all the promised features. The user stories are done, the test cases have passed, and the go/no-go meeting ends in a big green checkmark.
Then the complaints begin.
“It’s too slow.”
“I don’t trust the security.”
“Users can’t figure out how to do the simplest things.”
“Ops says they can’t see what’s going on under the hood.”
The problem is often not what the system does but how well it does it. In other words: the non-functional requirements were vague, hidden, or missing.
“We want it fast, secure, and easy to use” is not a specification. It’s a wish list.
This article is about turning that wish list into concrete non-functional requirements (NFRs) that developers actually design to, testers actually verify, and operations teams actually monitor. We’ll walk through a simple method, show examples in performance, security, usability, and operability, and end with a small checklist you can apply to your current project.
Functional vs Non-Functional: A Practical View
From a BA’s standpoint, the distinction is simple:
- Functional requirements describe what the system does.
- Non-functional requirements describe how well it does it and under what constraints.
For example:
- Functional: “The system displays the customer’s account balances.”
- Non-functional: “For at least 95% of requests between 6 p.m. and 10 p.m., the system displays the customer’s account balances within 2 seconds.”
That one extra sentence changes how the system is architected, how it’s tested, and how it’s monitored.
Non-functional requirements often fail in practice because they’re:
- Too abstract (“fast”, “secure”, “intuitive”),
- Not measurable,
- Not connected to stories, tests, or dashboards,
- Never validated with tech leads, testers, or ops.
The goal is not perfection; it’s to reach a point where each NFR is specific enough that a developer can design to it and a tester can say “pass” or “fail” with a straight face.
Step 1 – Decide Which Qualities Really Matter
Not every quality attribute matters equally on every project. You might care about performance, security, usability, reliability, availability, operability, maintainability, and more—but they won’t all be top priority.
A good starting question for stakeholders is:
“If all the features worked exactly as described, what could still make this system a failure?”
That question pulls out the real quality concerns. For an online customer self-service portal in a bank, the answers might cluster around:
- Performance: customers won’t tolerate a sluggish portal.
- Security: you’re dealing with PII and financial data.
- Usability: many users log in rarely and may not be tech-savvy.
- Operability: the portal needs to be up and diagnosable around the clock.
You don’t need a three-day workshop to prioritize. Get a small group together—product, tech lead, QA, someone from ops or support, and security if needed. Ask each person to pick the three quality attributes they think matter most. Where the votes cluster, that’s where you focus your NFR effort.
Step 2 – Capture Scenarios, Not Adjectives
Stakeholders naturally talk in adjectives: “fast”, “secure”, “intuitive”, “reliable”. Your job is to turn those adjectives into scenarios.
A simple template helps:
“In the context of [environment / usage], when [trigger], the system shall [response], measured by [metric / threshold].”
For example:
- Performance: “During peak evening hours, when customers check their account balance, the page should load within a couple of seconds.”
- Security: “Only staff in the ‘Loan Underwriting’ role should be able to view full credit reports.”
- Usability: “A first-time customer should be able to complete account registration without needing instructions.”
- Operability: “If the nightly batch fails, support should know quickly and see which job failed.”
At this stage you are not wordsmithing requirements, you’re collecting stories about quality. Ask things like:
- “When do users notice that it’s slow?”
- “What’s the worst thing that could happen if this data leaked?”
- “What does ‘easy to use’ mean for a first-time user?”
- “What does the on-call engineer need to see at 2 a.m. when something breaks?”
Those answers become the raw material for precise NFRs.
Step 3 – Turn Scenarios into Measurable Requirements
Once you have scenarios, you add numbers and clear conditions.
The main ingredients are:
- Time (seconds, minutes, hours),
- Percentages (90% of cases, 99.5% availability),
- Counts (concurrent users, max transactions),
- Roles/rights (who can do or see what).
Let’s look at some concrete examples.
Performance
The classic anti-pattern is:
“The system shall be fast.”
Here is a better version for a portal:
“For at least 95% of account summary requests between 6 p.m. and 10 p.m., the system shall display results within 2 seconds for up to 5,000 concurrent users in production.”
Another example for product search:
“Search results shall be returned within 3 seconds for at least 90% of searches, with up to 50 filters applied and a product catalog of up to 10,000 items.”
And one for throughput:
“The system shall process at least 10,000 completed transactions per hour in the production environment with a failure rate below 1% under normal operating conditions.”
These statements give architects and testers something concrete to aim at.
Security
“The system shall be secure” is not actionable. Consider this instead:
“All external web traffic shall be encrypted using TLS 1.2 or higher, with HTTP Strict Transport Security (HSTS) enabled for all public endpoints.”
Or for login protection:
“Users shall be locked out after 5 failed login attempts within 15 minutes, and each lockout event shall be logged with timestamp, IP address, and user identifier where available.”
For role-based access:
“Only users assigned the ‘Loan Underwriter’ role may view full credit report details. Other roles may see only the customer’s name and masked SSN (last 4 digits).”
Now security and development have a shared target.
Usability
“User-friendly” is probably the vaguest NFR phrase in existence. A more testable version for registration might be:
“In usability testing, at least 85% of first-time users shall complete the online account registration process within 5 minutes on their first attempt without external help.”
If accessibility is important:
“All interactive elements on the login, registration, and checkout pages shall be operable via keyboard only and shall comply with WCAG 2.1 AA guidelines.”
Even error messages can be specified:
“Error messages shall state the problem and one specific corrective action in 160 characters or fewer.”
These kinds of requirements can drive usability tests and design reviews.
Operability
“Easy to support” doesn’t tell ops what they’ll actually get. Compare that with:
“The system shall expose application health metrics—CPU usage, memory usage, error rate, and average response time—via a /health endpoint consumable by the standard monitoring tool.”
For logging:
“Application logs in production shall include timestamp, correlation ID, severity level, and user identifier (where applicable) for all errors and warnings.”
For alerts:
“For critical production incidents (Priority 1), an alert shall be sent to the on-call channel within 2 minutes of detection, including service name, environment, and a short error summary.”
For deployment:
“Deploying a new version to production shall not require more than 5 minutes of user-facing downtime per deployment.”
These are the kinds of statements that operations teams can design monitors and playbooks around.
Step 4 – Sanity Check with Dev, Test, and Ops
Before you declare your NFRs “done,” check them with the people who have to implement and validate them.
Share the draft NFRs with:
- A tech lead or architect,
- A QA or test lead,
- Someone from operations or SRE.
Then walk through a few questions:
- “How would you test this requirement?”
- “Is this realistic with our current architecture and budget?”
- “What tools or design changes would we need?”
- “If we loosened or tightened this threshold, what would it cost us?”
You’ll almost always end up adjusting at least some thresholds—2 seconds becomes 3 seconds, 99.9% availability becomes 99.5%, and so on. The value of this conversation is that trade-offs become explicit and written down, instead of being silently ignored.
At the end of this step, your NFRs are not just well-worded; they are owned by the people who will make them real.
Step 5 – Put NFRs Where People Will Actually See Them
Even the best NFRs won’t help if they’re buried in a forgotten appendix.
You want two things:
- A single place where the full NFR set lives (a catalog).
- Pointers from stories, tests, and dashboards back to that catalog.
Your NFR catalog might be a requirements tool, a Confluence page, or even a simple spreadsheet. The structure doesn’t have to be fancy. A very workable pattern is to list:
- An ID,
- A short label,
- The full requirement text,
- The quality attribute (performance, security, etc.),
- The system area or service it applies to.
Then, in your backlog and test assets, you reference these IDs:
- User stories or features reference related NFRs.
- Test cases reference the NFR they verify.
- Monitoring dashboards and alerts mention the NFRs they are there to enforce.
With this approach, you avoid the “NFR document nobody reads” problem and instead treat NFRs as part of the working ecosystem of artifacts.
Fixing Vague NFRs: A Before-and-After Clinic
To get a feel for the transformation, look at a few classic “bad” statements and their improved versions.
- Performance
- Before: “System shall have good performance.”
- After: “The system shall return customer profile data in 1.5 seconds or less for at least 95% of requests under a load of 3,000 concurrent sessions in production.”
- Security
- Before: “System shall be secure and compliant.”
- After: “Customer passwords shall be stored using bcrypt with a cost factor of at least 10, and no password values may be logged in any environment.”
- Usability
- Before: “User interface shall be intuitive.”
- After: “In usability testing, at least 80% of first-time users shall be able to complete a balance transfer without external help in 7 minutes or less.”
- Operability
- Before: “System shall be easy to monitor.”
- After: “Each microservice shall expose /ready and /live endpoints that respond within 500 milliseconds, for use by the container orchestrator’s health checks.”
- Availability
- Before: “System shall have high availability.”
- After: “The customer-facing web application shall achieve at least 99.5% availability per calendar month, excluding pre-agreed maintenance windows of up to 2 hours per month.”
You can use these examples as patterns. The underlying moves are the same every time: replace adjectives with numbers, add context, and make verification obvious.
A Simple Checklist for Reviewing NFRs
When you review a non-functional requirement—yours or someone else’s—run it through this short mental checklist:
- Is it clear and measurable?
Does it avoid vague words like “fast” or “intuitive” on their own, and does it include at least one number or threshold?
- Is the context visible?
Does it say when and where it applies—peak vs non-peak, production vs test, which type of user?
- Is it feasible and testable?
Could a tester design a concrete test from this? Has a developer or architect confirmed that it’s realistic?
- Is it traceable?
Does it have an ID, and is it linked to at least one story, use case, or epic?
- Is it stored where people can find it?
Is it part of a central catalog or repository, with changes tracked?
If you can honestly say “yes” to most of those questions, you’ve moved far beyond “The system shall be fast” and into requirements that will shape real design and testing decisions.
Bringing It Into Your Next Project
You don’t need a huge initiative to improve non-functional requirements. You can start this week:
- Pick a single project that’s already in progress.
- Find three to five vague non-functional statements.
- Rewrite them using the examples and patterns in this article.
- Walk them past a tech lead, a tester, and someone from ops.
- Hook them into your stories, tests, and monitoring.
You’ll quickly notice a shift. Conversations become sharper. Trade-offs are surfaced earlier. And when the system goes live, you’ll spend less time saying “Well, that’s what the stories said,” and more time hearing, “This behaves the way we expected.”
That’s when you know your non-functional requirements have become something developers actually use—not because they love documentation, but because the documentation finally helps them build the right thing, the right way.
Author: Morgan Masters, Business Analyst, Modern Analyst Media LLC
Morgan Masters is Business Analyst and Staff Writer at ModernAnalyst.com, the premier community and resource portal for business analysts. Business analysis resources such as articles, blogs, templates, forums, books, along with a thriving business analyst community can be found at http://www.ModernAnalyst.com