SvelteKit Production Deployment - AI-Optimized Knowledge Base

Critical Configuration Requirements

Adapter Selection

NEVER use adapter-auto in production

• Problem: Environment variable detection timing failures in CI
• Impact: 3+ hour debugging sessions for "Could not detect supported environment" errors
• Solution: Use platform-specific adapters

// Production-safe configuration
import adapter from '@sveltejs/adapter-vercel';
// OR @sveltejs/adapter-netlify, @sveltejs/adapter-node

Environment Variables - Production Failures

Build-time validation prevents runtime disasters

• Critical Issue: Variables work locally but fail in production due to scope violations
• Detection: ERROR: 'VARIABLE_NAME' is not exported by $env/static/private
• Root Cause: Client components accessing private variables

// Centralized validation system
const requiredVars = { PRIVATE_API_KEY, PRIVATE_DB_URL };
Object.entries(requiredVars).forEach(([name, value]) => {
  if (!value) throw new Error(`Missing: ${name}`);
});

Memory Management - Critical Production Issues

Server Load Function Memory Leaks

Frequency: Kills containers after days of operation
Detection: Gradual memory increase until restart
Root Cause: Development server restarts hide persistent memory accumulation

// DANGEROUS - Memory leak pattern
const globalCache = new Map(); // Never cleaned

// SAFE - Size-limited cache
import { LRUCache } from 'lru-cache';
const cache = new LRUCache({ max: 500, ttl: 600000 });

Platform-Specific Failure Modes

Platform	Critical Failures	Root Cause	Fix Difficulty	Time Investment
Vercel	Edge Runtime API limits	Node.js APIs unavailable in Edge	Easy	1-2 hours
Netlify	10-second function timeouts	Hard serverless limits	Medium	4-6 hours
CloudFlare	Module resolution failures	Workers runtime differences	Hard	8+ hours
Self-hosted	Everything breaks uniquely	Infrastructure complexity	Nightmare	Days to weeks

Vercel Edge Runtime Limitations

Breaking APIs: fs, path, crypto modules
Detection: Local success, production 500 errors
Workaround: Dynamic imports with environment checks

Netlify Function Constraints

Hard Limit: 10 seconds execution time
Impact: Heavy database operations fail silently
Mitigation: Move to background functions or static generation

Docker Production Configuration

Multi-stage Build Requirements

FROM node:18-alpine as build
COPY package*.json ./
RUN npm ci --only=production=false
COPY . .
RUN npm run build
RUN npm ci --only=production && npm cache clean --force

FROM node:18-alpine as production
RUN adduser -S sveltekit -u 1001
COPY --from=build --chown=sveltekit:nodejs /app/build ./build
USER sveltekit
CMD ["node", "build/index.js"]

Critical Elements:

• Separate build/production stages prevent dev dependencies in final image
• Non-root user prevents security vulnerabilities
• Explicit dependency cleanup reduces image size by 60-80%

Client-Side Routing Configuration

Static Host Requirements

Problem: Direct URL access returns 404 errors
Impact: Breaks user bookmarks and social sharing
Frequency: 100% of static deployments without configuration

Server Configurations

# Nginx
location / { try_files $uri $uri/ @fallback; }
location @fallback { rewrite ^.*$ /index.html last; }

# Apache
RewriteEngine On
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule . /index.html [L]

Build Timeout Prevention

Vercel 45-minute Timeout

Triggers:

• Dependency resolution conflicts
• Memory exhaustion during TypeScript compilation
• Node.js version mismatches

Solutions:

{
  "scripts": {
    "build": "NODE_OPTIONS='--max-old-space-size=4096' vite build"
  },
  "engines": { "node": ">=18.0.0" }
}

Database Connection Management

Production Connection Pooling

Development Pattern: Single connections work
Production Reality: Database dies under concurrent load
Required Configuration:

const db = createPool({
  max: 20,
  idleTimeoutMillis: 30000,
  connectionTimeoutMillis: 2000
});

Error Handling - Production vs Development

Error Boundary Requirements

Development: Nice error pages with stack traces
Production: Blank pages or exposed internals

// Production-safe error handling
export async function handleError({ error: err }) {
  if (err.message.includes('DATABASE') || err.message.includes('API_KEY')) {
    return { message: 'Internal server error', code: 'GENERIC_ERROR' };
  }
  return { message: err.message, code: err.code };
}

Nuclear Option: Static Generation

When Everything Else Fails

Trade-off: Lose SSR benefits, eliminate 90% of deployment issues
Use Case: Complex server-side logic causing persistent failures

import adapter from '@sveltejs/adapter-static';
export default {
  kit: {
    adapter: adapter({
      fallback: '200.html', // SPA fallback
      precompress: false
    }),
    prerender: { entries: ['*'] }
  }
};

Common Failure Patterns and Detection

Build Success, Runtime Failure

Pattern: "Build successful" but users see blank pages
Root Cause: Client/server variable scope mismatch
Detection: Private variables accessed in client components

Authentication Breaks After Deployment

Cause: Session storage location changes
Development: Filesystem storage works
Production: Requires persistent storage (database/Redis)

Random CloudFlare Deployment Failures

Pattern: Works sometimes, fails randomly
Cause: Edge runtime instability
Solution: Avoid Node.js-specific APIs entirely

Resource Requirements and Time Investment

Debugging Time by Issue Type

• Adapter-auto failures: 3-6 hours initial troubleshooting
• Environment variable scope: 2-4 hours if patterns not understood
• Memory leaks: 1-2 days to identify, 2-4 hours to fix
• Platform-specific failures: 4-8 hours per platform
• Docker configuration: 6-12 hours for production-ready setup

Expertise Requirements

• Basic deployment: Understanding of build processes and environment variables
• Production troubleshooting: Knowledge of platform-specific limitations
• Memory optimization: Understanding of Node.js garbage collection
• Security hardening: Container security and user permissions

Essential Resources for Production Success

Critical Documentation

• SvelteKit Adapters: Why adapter-auto fails, how to choose correctly
• Environment Variables Guide: Scope differences between static/dynamic, public/private
• Vercel SvelteKit Docs: Best platform-specific documentation

Community Solutions

• GitHub Issue #2956: Adapter-auto detection failures
• GitHub Issue #7066: Environment variable build errors
• SvelteKit Discord #sveltekit-help: Real-time community support

Breaking Points and System Limits

Memory Limits

• Vercel: 3008MB maximum, build timeouts at 45 minutes
• Netlify: 10-second function timeout, no configuration override
• CloudFlare: 128MB memory limit, 50ms CPU limit

Performance Thresholds

• UI Responsiveness: Breaks at 1000+ concurrent spans in tracing
• Build Performance: TypeScript compilation fails above 4GB memory usage
• Database Connections: Production failure above 20 concurrent connections without pooling

Cost Implications

• Platform switching: 1-3 days development time per migration
• Memory leak fixes: 2-4 hours implementation + 1-2 weeks monitoring
• Security hardening: 4-8 hours initial setup + ongoing maintenance

Decision Criteria for Platform Selection

Choose Vercel if:

• Need edge runtime performance
• Have <45 minute build times
• Can work within Edge Runtime API limitations

Choose Netlify if:

• Server functions under 10 seconds
• Need form handling capabilities
• Static-first architecture

Choose Self-hosted if:

• Need full control over infrastructure
• Have dedicated DevOps expertise
• Long-term cost optimization priority

Choose Static Generation if:

• Deployment complexity exceeds benefit threshold
• Server-side features not critical
• Maximum reliability priority over dynamic features