Answer
Nested promises can monopolize the microtask queue, blocking I/O. Break chains with setImmediate or timers to restore fairness.
Quick Answer
Each Promise.then() creates a microtask. When that microtask runs, if it returns another Promise, the resolution of that inner Promise schedules another microtask — before any macrotask (I/O, setTimeout) runs. Deep promise chains with synchronous inner Promises can fill the microtask queue deeply, delaying I/O callbacks noticeably.
S
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