It increases latency (you wait for multiple calls), increases failure probability (one dependency failing breaks the whole request), and can amplify load. Reduce it by aggregating in a BFF/API Gateway, caching, using async/event-driven flows, and by setting timeouts + bulkheads so one slow dependency doesn’t stall everything.
Expanding on the short answer — what usually matters in practice:
A tiny example (an explanation template):
// Example: discuss trade-offs for "why-is-synchronous-fan-out-(one-request-calling-"
function explain() {
// Start from the core idea:
// It increases latency (you wait for multiple calls), increases failure probability (one dep
}