chapter two

2 Measure the real cost of slow performance

 

This chapter covers

  • How slow performance affects discovery before users arrive
  • The internal costs caused by slow systems
  • Framing performance issues for stakeholders
  • Running your first performance cost analysis

Speed is the foundation of a good user experience. When a product responds quickly, users feel in control, they develop trust in it, and that trust brings them back. When delays creep in, even small ones, confidence begins to erode, and engagement and revenue tend to follow.

For engineers, this matters because even small delays can impact the number of people who complete their tasks, whether the slowdown originates from an API call, a heavy UI component, or an inefficient query. For tech leads and senior engineers, it influences the patterns you encourage and how you decide what the team should focus on next. For engineering managers, it shapes staffing decisions, risk, and how you balance new features with keeping the product healthy. Slow performance is never an abstract problem; it affects how easily people find your product, how much they use it, and the lengthy support and rework that follow when things slow down.

2.1 When seconds cost millions

2.1.1 Web and mobile: The checkout regression

2.1.2 Backend: The API degradation

2.1.3 Desktop: The rendering regression

2.1.4 The common pattern

2.2 The discovery cost of being slow

2.2.1 Web: Search rankings and acquisition

2.2.2 Mobile: App store visibility and ratings

2.2.3 Backend: Proof-of-concept trials and enterprise adoption

2.3 The hidden costs

2.3.1 Productivity

2.3.2 Morale

2.3.3 Inclusion

2.3.4 Collaboration

2.3.5 Infrastructure

2.4 Making the case for speed

2.5 Quantifying the cost: A step-by-step analysis

2.5.1 Step 1: Choose a high-value flow and find the baseline

2.5.2 Step 2: Tie the flow to value

2.5.3 Step 3: Model and calculate the impact

2.5.4 Step 4: Present the cost clearly

2.5.5 Repeating the exercise

2.6 Summary