Answer
Synchronous operations block the event loop until the task completes. Asynchronous operations allow Node to continue handling other requests while the file task runs in the background. Async is preferred to avoid blocking.
Quick Answer
Sync file ops (readFileSync, writeFileSync) block the event loop — the entire Node.js process freezes until the file operation completes. No other requests can be handled during that time. Async file ops (readFile, writeFile) hand the work off to libuv, return immediately, and call your callback when done. In a web server, always use async.
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SugharaIQ Editorial Team
Verified Answer
This answer has been peer-reviewed by industry experts holding senior engineering roles to ensure technical accuracy and relevance for modern interview standards.
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Source: SugharaIQ