Performance Optimization Trade-offs
Balancing performance optimizations with development complexity and user experience.
Quick Navigation: Code Splitting • Lazy Loading • Bundle Size • Images • Core Web Vitals
The Performance Trade-off Triangle
Every performance optimization involves trade-offs between:
- Initial Load: Time to first meaningful paint
- Runtime Performance: Responsiveness during interaction
- Developer Experience: Complexity and maintainability
Code Splitting Strategies
Route-Based Splitting
Split code by page/route. Each route loads its own bundle.
Pros
- ✓ Natural split points
- ✓ Easy to implement (Next.js automatic)
- ✓ Good for large apps
Cons
- ✗ Loading delay on navigation
- ✗ May not be enough for large pages
Component-Based Splitting
Split heavy components (modals, charts, editors).
Pros
- ✓ Fine-grained control
- ✓ Load only when needed
- ✓ Smaller initial bundle
Cons
- ✗ More complex implementation
- ✗ Need loading states
- ✗ Can cause layout shift
Vendor Splitting
Separate third-party libraries into their own chunk.
Pros
- ✓ Better caching (vendors rarely change)
- ✓ Parallel loading
Cons
- ✗ Additional HTTP requests
- ✗ May increase total bytes
Lazy Loading Trade-offs
Eager Loading
Load everything upfront.
🎯 Best For: Small apps, critical features
Lazy Loading
Load on demand (visibility, interaction).
🎯 Best For: Large apps, below-fold content
Lazy Loading Triggers
On Visibility
Load when element enters viewport (Intersection Observer)
On Interaction
Load on hover, click, or focus
On Idle
Load when browser is idle (requestIdleCallback)
Bundle Size vs Features
Library Selection Trade-offs
| Need | Heavy Option | Light Option |
|---|---|---|
| Date handling | Moment.js (~70KB) | date-fns (~7KB tree-shaken) |
| State management | Redux (~15KB) | Zustand (~1KB) |
| Animation | Framer Motion (~50KB) | CSS animations (0KB) |
| UI Components | Material UI (~100KB+) | Radix + Tailwind (~20KB) |
Tree Shaking Considerations
- Named imports:
import { specific } from 'lib'- tree-shakeable - Default imports:
import lib from 'lib'- often includes everything - Side effects: Some libraries have side effects that prevent tree shaking
Image Optimization
Format Trade-offs
| Format | Best For | Trade-off |
|---|---|---|
| WebP | Most images (photos, graphics) | 30% smaller than JPEG/PNG |
| AVIF | Highest compression | Limited browser support |
| SVG | Icons, logos, illustrations | Complex SVGs can be large |
| JPEG | Photos (fallback) | Larger, lossy compression |
Loading Strategies
Eager (Above the fold)
- • Priority loading for LCP images
- • Use preload for critical images
- • Avoid layout shift with dimensions
Lazy (Below the fold)
- • Native:
loading="lazy" - • Placeholder with blur-up
- • Intersection Observer for control
Core Web Vitals Trade-offs
LCP (Largest Contentful Paint)
Time until largest content element is visible.
Optimize
- • Preload LCP image
- • Optimize server response time
- • Use CDN for static assets
Trade-off
- • More preloads = more bandwidth
- • SSR adds server complexity
INP (Interaction to Next Paint)
Responsiveness to user interactions.
Optimize
- • Break up long tasks
- • Use web workers for heavy computation
- • Debounce/throttle handlers
Trade-off
- • More complex code architecture
- • Web workers add overhead
CLS (Cumulative Layout Shift)
Visual stability - elements shifting unexpectedly.
Optimize
- • Reserve space for dynamic content
- • Set explicit image dimensions
- • Avoid inserting content above existing
Trade-off
- • Skeleton screens add complexity
- • Fixed dimensions limit flexibility
Best Practices
- 1.Measure first. Use Lighthouse, WebPageTest, or RUM before optimizing.
- 2.Prioritize user-perceived performance. LCP and INP matter most.
- 3.Use framework features. Next.js Image, automatic code splitting.
- 4.Avoid premature optimization. Ship first, optimize based on data.
- 5.Set performance budgets. Fail CI if bundle exceeds threshold.