Common performance bottlenecks in Node.js include:

• Blocking I/O: Since Node.js is single-threaded, blocking I/O operations like synchronous file reads can cause bottlenecks. To optimize, use asynchronous methods like fs.readFile.
• Memory Leaks: Use tools like node-inspect or clinic.js to track memory usage and optimize memory management.
• Database Queries: Inefficient queries or unindexed databases can slow down response times. Always optimize queries and add appropriate indexes.
• Too many concurrent requests: Use tools like PM2 to load balance and scale the application horizontally.