Performance Optimization

Performance optimization strategies and best practices for DesQTA

Performance Overview

DesQTA is optimized for fast load times, smooth interactions, and efficient resource usage. This guide covers optimization strategies and best practices.

Frontend Optimizations

Code Splitting

SvelteKit automatically splits code by route:

// Lazy load heavy components
const HeavyComponent = lazy(() => import('./HeavyComponent.svelte'));

// Dynamic imports for routes
const module = await import('./heavy-module.js');

Component Lazy Loading

<script lang="ts">
  import { onMount } from 'svelte';
  
  let ChartComponent: any = null;
  
  onMount(async () => {
    // Load only when needed
    const module = await import('./Chart.svelte');
    ChartComponent = module.default;
  });
</script>

{#if ChartComponent}
  <svelte:component this={ChartComponent} {data} />
{/if}

Virtual Scrolling

For long lists, use virtual scrolling:

<script lang="ts">
  import { VirtualList } from 'svelte-virtual-list';
  
  let items = $state<Item[]>([]);
</script>

<VirtualList
  items={items}
  itemHeight={50}
  let:item
>
  <div>{item.name}</div>
</VirtualList>

Debouncing and Throttling

Debounce expensive operations:

<script lang="ts">
  import { debounce } from '$lib/utils/helpers';
  
  let searchQuery = $state('');
  
  const debouncedSearch = debounce((query: string) => {
    performSearch(query);
  }, 300);
  
  function handleInput(e: Event) {
    const target = e.target as HTMLInputElement;
    searchQuery = target.value;
    debouncedSearch(searchQuery);
  }
</script>

<input type="text" oninput={handleInput} />

Memoization

Use $derived for computed values:

<script lang="ts">
  let items = $state<Item[]>([]);
  let filter = $state('');
  
  // ✅ Good - Memoized
  let filteredItems = $derived(
    items.filter(item => item.name.includes(filter))
  );
  
  // ❌ Avoid - Recomputes every render
  let filteredItems = items.filter(item => item.name.includes(filter));
</script>

Caching Strategies

Memory Cache

Use in-memory cache for frequently accessed data:

import { cache } from '$lib/utils/cache';

async function getData(key: string) {
  // Check cache first
  if (cache.has(key)) {
    return cache.get(key);
  }
  
  // Fetch and cache
  const data = await fetchData();
  cache.set(key, data, 5 * 60 * 1000); // 5 minutes
  return data;
}

IndexedDB Cache

Persistent cache for offline support:

import { idbCache } from '$lib/services/idbCache';

async function getCachedData(key: string) {
  const cached = await idbCache.get(key);
  if (cached && !isExpired(cached)) {
    return cached.data;
  }
  
  const data = await fetchData();
  await idbCache.set(key, data, Date.now() + 60 * 60 * 1000);
  return data;
}

Service Worker Cache

Cache static assets and API responses:

// Cache API responses
self.addEventListener('fetch', (event) => {
  if (event.request.url.includes('/api/')) {
    event.respondWith(
      caches.match(event.request).then((response) => {
        return response || fetch(event.request).then((response) => {
          const clone = response.clone();
          caches.open('api-cache').then((cache) => {
            cache.put(event.request, clone);
          });
          return response;
        });
      })
    );
  }
});

Image Optimization

Lazy Loading Images

<img
  src={imageUrl}
  loading="lazy"
  alt="Description"
/>

Responsive Images

<img
  srcset="
    image-small.jpg 480w,
    image-medium.jpg 768w,
    image-large.jpg 1200w
  "
  sizes="(max-width: 480px) 100vw, (max-width: 768px) 50vw, 33vw"
  src="image-medium.jpg"
  alt="Description"
/>

Image Compression

Use optimized image formats:

  • WebP: Modern format with better compression
  • AVIF: Next-generation format (when supported)
  • Lazy load: Load images only when visible

Bundle Optimization

Tree Shaking

Remove unused code:

// ✅ Good - Import only what you need
import { debounce } from '$lib/utils/helpers';

// ❌ Avoid - Import entire module
import * as utils from '$lib/utils/helpers';

Minimize Dependencies

// ✅ Good - Lightweight alternative
import { format } from 'date-fns';

// ❌ Avoid - Heavy library
import moment from 'moment';

Code Splitting by Feature

// Load features on demand
if (featureEnabled) {
  const FeatureModule = await import('./Feature.svelte');
}

Rendering Optimization

Avoid Unnecessary Re-renders

<script lang="ts">
  // ✅ Good - Stable reference
  const config = { theme: 'dark' };
  
  // ❌ Avoid - New object every render
  const config = { theme: 'dark' }; // Creates new object
</script>

Use Keyed Each Blocks

<!-- ✅ Good - Keyed -->
{#each items as item (item.id)}
  <ItemComponent {item} />
{/each}

<!-- ❌ Avoid - Not keyed -->
{#each items as item}
  <ItemComponent {item} />
{/each}

Conditional Rendering

<!-- ✅ Good - Early return -->
{#if !loading}
  {#if data}
    <DataComponent {data} />
  {:else}
    <EmptyState />
  {/if}
{/if}

<!-- ❌ Avoid - Nested conditions -->
{#if loading}
  <LoadingSpinner />
{:else if data}
  <DataComponent {data} />
{:else}
  <EmptyState />
{/if}

Network Optimization

Request Deduplication

Prevent duplicate requests:

const pendingRequests = new Map<string, Promise<any>>();

async function fetchData(key: string) {
  if (pendingRequests.has(key)) {
    return pendingRequests.get(key);
  }
  
  const promise = fetch(key).then(res => res.json());
  pendingRequests.set(key, promise);
  
  try {
    const result = await promise;
    return result;
  } finally {
    pendingRequests.delete(key);
  }
}

Request Batching

Batch multiple requests:

async function batchRequests(requests: Promise<any>[]) {
  return Promise.all(requests);
}

Connection Pooling

Reuse HTTP connections (handled by Tauri backend).

Memory Management

Cleanup Subscriptions

<script lang="ts">
  import { onDestroy } from 'svelte';
  
  const unsubscribe = store.subscribe(value => {
    // Handle update
  });
  
  onDestroy(() => {
    unsubscribe();
  });
</script>

Remove Event Listeners

<script lang="ts">
  import { onMount, onDestroy } from 'svelte';
  
  let handler: (() => void) | null = null;
  
  onMount(() => {
    handler = () => {
      // Handle event
    };
    window.addEventListener('resize', handler);
  });
  
  onDestroy(() => {
    if (handler) {
      window.removeEventListener('resize', handler);
    }
  });
</script>

Clear Intervals/Timeouts

<script lang="ts">
  import { onMount, onDestroy } from 'svelte';
  
  let interval: ReturnType<typeof setInterval>;
  
  onMount(() => {
    interval = setInterval(() => {
      // Update
    }, 1000);
  });
  
  onDestroy(() => {
    clearInterval(interval);
  });
</script>

Performance Monitoring

Performance Metrics

Track key metrics:

// Time to Interactive (TTI)
const tti = performance.timing.domInteractive - performance.timing.navigationStart;

// First Contentful Paint (FCP)
const fcp = performance.getEntriesByType('paint')[0].startTime;

// Largest Contentful Paint (LCP)
const lcp = performance.getEntriesByType('largest-contentful-paint')[0].startTime;

Custom Performance Marks

// Mark start
performance.mark('data-load-start');

// Load data
await loadData();

// Mark end and measure
performance.mark('data-load-end');
performance.measure('data-load', 'data-load-start', 'data-load-end');

// Get measurement
const measure = performance.getEntriesByName('data-load')[0];
console.log(`Data load took ${measure.duration}ms`);

Logging Performance

import { logger } from '$lib/utils/logger';

async function loadData() {
  const startTime = performance.now();
  
  try {
    const data = await fetchData();
    const endTime = performance.now();
    logger.logPerformance('service', 'loadData', startTime, endTime);
    return data;
  } catch (error) {
    logger.error('service', 'loadData', 'Failed', { error });
    throw error;
  }
}

Best Practices

1. Measure Before Optimizing

// Profile first
console.time('operation');
await expensiveOperation();
console.timeEnd('operation');

2. Optimize Critical Path

Focus on:

  • Initial page load
  • User interactions
  • Data fetching

3. Use Production Builds

# Development - Not optimized
npm run dev

# Production - Optimized
npm run build

4. Monitor Bundle Size

# Analyze bundle
npm run build -- --analyze

5. Test Performance

// Performance tests
test('loads page in under 2 seconds', async () => {
  const start = performance.now();
  await page.goto('/');
  const duration = performance.now() - start;
  expect(duration).toBeLessThan(2000);
});

Performance Checklist

  • Code splitting implemented
  • Images optimized and lazy loaded
  • Caching strategy in place
  • Debouncing/throttling applied
  • Unused code removed
  • Memory leaks prevented
  • Performance metrics tracked
  • Production builds optimized

Next Steps

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Testing Guide
Testing strategies, patterns, and best practices for DesQTA
Error Handling
Error handling patterns and best practices in DesQTA