Fresh Performance Optimization: AI-Optimized Technical Reference

Critical Performance Specifications

Fresh 2.0 vs 1.x Performance Impact

• Boot time: 9-12x faster (86ms → 8ms production measured)
• Cold starts: 45-60x better than traditional serverless
• HMR: Full page reloads eliminated in development
• Bundle optimization: Server code bundles for faster file resolution
• Migration requirement: Must upgrade to Fresh 2.0 beta for performance gains

Breaking Performance Thresholds

• Memory limits: 128MB free tier, 512MB paid (Deno Deploy)
• Bundle size: 1MB limit on Cloudflare Workers
• Response time targets: <100ms (optimal), >500ms indicates serious issues
• Database query targets: <50ms average
• JavaScript bundle: Keep <50KB for optimal performance

Configuration That Actually Works in Production

Islands Architecture - Critical Implementation Rules

DO make islands:

• Form components with validation (~8KB each)
• Interactive buttons, toggles, modals (~3KB each)
• Real-time data components (chat, notifications)
• Client-side routing within components

DON'T make islands:

• Static content that never changes
• Navigation menus (unless dropdowns required)
• Footer links and contact information
• Blog post content

Performance impact: Each unnecessary island adds 3-8KB JavaScript. 10 pointless islands = 80KB bundle bloat.

Database Connection Management

// PRODUCTION CONFIGURATION - Connection pooling required
const pool = new Pool({
  database: "mydb",
  hostname: "localhost", 
  port: 5432,
  user: "user",
  password: "password",
}, 3, true);

// Critical: Release connections explicitly
const client = await pool.connect();
const data = await client.queryArray("SELECT * FROM users");
client.release(); // Required or memory leaks occur

Route Loading Optimization

// AVOID - Heavy imports in route files cause 500KB+ loads
import { HugeLibrary } from "npm:massive-library@latest";

// IMPLEMENT - Lazy load heavy dependencies
export default function Index() {
  return <LazyHeavyComponent />; // Load only when needed
}

Resource Requirements & Real Costs

Platform Performance Characteristics

Platform	Cold Start	Memory Limit	Bundle Limit	Best Use Case	Fresh Compatibility
Deno Deploy	8ms (2.0)	128MB/512MB	No limit	Edge performance	Perfect
Cloudflare Workers	10-30ms	128MB	1MB compressed	Global distribution	Good with caveats
AWS Lambda	50-200ms	3GB max	50MB	Enterprise	Loses edge benefits
Self-hosted	Hardware dependent	Unlimited	Unlimited	Full control	Defeats architecture

Time Investment Requirements

• Fresh 1.x → 2.0 migration: 2-4 hours for typical app
• Islands architecture refactoring: 1 day for improperly structured app
• Database optimization: 4-8 hours for connection pooling implementation
• Bundle analysis and optimization: 2-4 hours initial, 1 hour maintenance

Expertise Prerequisites

• Required: Understanding of Islands Architecture principles
• Critical: Database connection management on edge platforms
• Essential: Deno runtime differences from Node.js
• Helpful: Preact vs React performance characteristics

Critical Warnings & Failure Modes

What Documentation Doesn't Tell You

Environment variable sync delay: 30 seconds on Deno Deploy after changes. Connection string updates aren't immediate.

Edge function connection loss: More frequent than traditional servers. Always implement connection retry logic.

npm package Node.js dependencies: Break at runtime or bloat bundles. Use deno info --json main.ts to audit imports.

React vs Preact import confusion: Accidentally importing React instead of Preact adds 45KB to bundle.

Common Production Failures

UI breaks at 1000+ spans: Makes debugging large distributed transactions impossible. No workaround available.

Memory exhaustion patterns:

• Large data structures kept in memory
• Database connections not properly closed
• Image processing without cleanup
• Infinite cache growth

Bundle size explosion: Each React ecosystem library significantly increases bundle size, negating Fresh's performance benefits.

Database Query Failure Scenarios

• Connection pooling absence: New connection per request causes 200ms+ response times
• Edge database location mismatch: Cross-region queries add 100-300ms latency
• Query complexity without indexes: Can cause 1000ms+ response times

Implementation Reality

Default Settings That Fail in Production

• Single database connection without pooling
• No image optimization (2MB+ images kill performance)
• All components as islands by default
• npm packages without Deno compatibility checks

Actual vs Documented Behavior

• Fresh "zero JavaScript": Only applies to static content, not islands
• Hot Module Replacement: Only works properly in Fresh 2.0
• Edge deployment speed: Database queries often bottleneck, not framework
• Bundle optimization: Requires manual audit of npm dependencies

Community Support Quality

• Fresh 2.0: Beta status, active development, breaking changes possible
• Deno ecosystem: Smaller than Node.js, fewer third-party solutions
• Edge platform debugging: Limited compared to traditional server environments

Decision Support Information

Fresh vs Alternatives Trade-offs

Choose Fresh when:

• Edge performance is critical
• Static-heavy content with selective interactivity
• Deno ecosystem alignment acceptable
• Team comfortable with newer technology

Avoid Fresh when:

• Heavy React ecosystem dependencies required
• Complex client-side state management needed
• Traditional server deployment required
• Team lacks Deno experience

Migration Pain Points

• Fresh 1.x → 2.0: Plugin API changes, import map modifications
• React → Preact: Some React-specific features unavailable
• Node.js → Deno: Different module resolution, API differences
• Traditional → Edge: Database connection patterns require complete rework

Hidden Costs

• Learning curve: 1-2 weeks for Node.js developers
• Ecosystem limitations: Fewer packages than npm
• Debugging complexity: Edge environments harder to debug locally
• Vendor lock-in risk: Deno Deploy is primary optimization target

Troubleshooting Decision Matrix

Performance Issue → Root Cause → Solution

Boot time >500ms:

• Root cause: Large npm packages at startup
• Solution: Audit with deno info, lazy load dependencies

High memory usage:

• Root cause: Unclosed database connections
• Solution: Implement connection pooling, explicit cleanup

Large bundle size:

• Root cause: Too many islands or React imports
• Solution: Convert static content to components, use Preact APIs

Slow database queries:

• Root cause: No connection pooling or missing indexes
• Solution: Implement Pool class, add database indexes

Development vs production performance gap:

• Root cause: Local cache vs remote dependencies
• Solution: Test in staging environment matching production constraints

Quantified Impacts & Thresholds

Performance Improvements (Measured)

• Fresh 2.0 upgrade: 9-12x boot time improvement
• Proper islands usage: 200ms → 18ms average response time
• Connection pooling: Eliminates 100-300ms connection overhead
• Image optimization: 80% file size reduction with WebP

Resource Usage Benchmarks

• Typical Fresh app: ~40MB memory usage at 15k requests/day
• Single island: 3-8KB JavaScript overhead
• Database query: Should average <50ms
• Bundle target: <50KB JavaScript for optimal performance

Failure Indicators

• >100ms response time: Investigate database queries first
• >64MB memory usage: Check for connection leaks
• >500ms boot time: Audit npm package imports
• Bundle >100KB: Review island necessity and React imports