JavaScript Runtime Comparison: Bun vs Deno vs Node.js - Production Reality

Configuration & Performance

HTTP Server Performance (Real-World)

Runtime	Hello World	Express/Framework	With Database	Production Reality
Bun 1.2+	50k RPS	25k RPS	8k RPS	3x faster when stable
Deno 2.0	30k RPS	20k RPS	7k RPS	20% slower than Node
Node.js 22	25k RPS	18k RPS	6k RPS	Predictable baseline

Container Sizes

• Bun: 80MB (efficient but debugging-hostile)
• Deno: 60MB (clean, single binary)
• Node.js: 300MB+ (bloated but battle-tested)

Memory & Startup

• Bun: Almost instant startup, efficient memory usage
• Deno: Fast startup, reasonable memory
• Node.js: 3-5 seconds startup, 200MB+ baseline memory

Critical Warnings & Failure Modes

Bun Stability Issues

• Pre-1.2.0: Crashed every 20 minutes with SIGSEGV
• Current (1.2+): Most stability issues resolved but still finding edge cases
• Native modules: ~10% failure rate with packages like sharp, bcrypt
• Error messages: Useless JavaScriptCore assembly dumps
• Crypto module: Different buffer initialization than V8, requires rewrites

Deno Permission Hell

• Security model: Brilliant in theory, exhausting in practice
• Reality: Most developers type --allow-all after 30 minutes
• Required flags: --allow-read --allow-write --allow-net --allow-env --allow-run
• Debugging permissions: Nightmare to determine which specific permission needed

Node.js Known Pain Points

• Memory leaks: Can take months to surface but debuggable
• Dependency hell: npm audit security nightmares
• node_modules: Will consume entire SSD given time
• Package bloat: 47 CSV parsers, half unmaintained since 2018

TypeScript Implementation Reality

Deno (Best)

• No build step: Direct .ts execution
• Type checking: Stricter than tsc, catches real bugs
• Source maps: Perfect debugging experience
• Downside: Strict checking breaks loose npm packages (200+ type errors)

Bun (Fast but Broken)

• Execution: Runs .ts files without transpilation
• Debugging: No source maps, impossible to debug type errors
• JavaScriptCore quirks: Different behavior than V8-optimized packages

Node.js (Predictable)

• Setup: Everyone knows tsc configuration
• Tooling: All debuggers work correctly
• Stack Overflow: 15 years of documented solutions

Package Compatibility Assessment

Bun Compatibility

• Success rate: 9/10 packages work
• Failure impact: 1/10 will completely break sprint
• Common failures: Native modules (bcrypt, sharp, crypto-related)
• JavaScriptCore differences: 15 years of V8-specific optimizations broken
• Debug time: 6+ hours for crypto module rewrites

Deno npm Integration

• Deno 2.0: Better than expected through compatibility layer
• Silent failures: Packages assuming Node.js behavior
• Import complexity: Need import maps for npm packages
• URL imports: Elegant but debugging offline dependency resolution is hard

Node.js Ecosystem

• Package availability: Every package ever made
• Quality variance: Massive but includes unmaintained packages
• Security: Regular audit vulnerabilities but solutions exist

Resource Requirements & Migration Costs

Development Team Impact

• Node.js hiring: Millions of available developers
• Bun expertise: <10 production experts globally
• Deno talent: Small but high-quality pool, 20% salary premium

Migration Time Investment

• Bun migration: 0 changes for simple apps, weeks for complex dependencies
• Deno migration: Moderate effort for permission configuration
• Production debugging: Node.js (hours), Deno (manageable), Bun (days)

Infrastructure Costs

• Cold starts: Bun 100-150ms, Deno 200-300ms, Node.js 400-500ms
• Lambda cost impact: Significant for millions of invocations
• Monitoring integration: Node.js (universal), Deno (basic), Bun (minimal)

Production Risk Assessment

Risk Factor	Bun	Deno	Node.js
Random crashes	High (still beta-testing)	Low	Very Low
3AM debugging	Very High	Medium	Low
Ecosystem gaps	High	Medium	None
Team onboarding	Very High	Medium	Low
Vendor lock-in	Low	Medium (Deploy platform)	None

Decision Criteria

Choose Bun When:

• CPU-intensive workloads where 3x performance gain justifies debugging costs
• Senior team comfortable with bleeding-edge tools
• Can absorb 6+ hour debugging sessions for native module issues
• New projects without complex dependency chains

Choose Deno When:

• TypeScript-first development with security requirements
• Building from scratch without legacy Node.js dependencies
• Team values code quality over ecosystem maturity
• Can work within permission system constraints

Choose Node.js When:

• Existing production applications (never rewrite working code)
• Enterprise compliance and monitoring requirements
• Need to hire developers quickly
• 3AM reliability more important than benchmark performance
• Startup where shipping speed > runtime optimization

Breaking Points & Hard Limits

Bun Blockers

• Native modules requiring V8-specific behavior
• Applications requiring reliable error reporting
• Teams without senior debugging expertise
• Production environments requiring 99.9% uptime

Deno Constraints

• Heavy npm dependency usage
• Teams unwilling to learn permission system
• Applications requiring extensive file system access
• Legacy codebases with Node.js-specific patterns

Node.js Limitations

• Applications where cold start time is critical cost factor
• Memory-constrained environments (serverless with high concurrency)
• Projects where TypeScript build complexity is development bottleneck

Critical Resources

• Bun Compatibility Tracker - Check before any migration
• Bun GitHub Issues - Essential for debugging crashes
• Deno Permission Documentation - Understand before deployment
• SaltyAom's Benchmark Repo - Only reproducible performance data