When is linear search acceptable in production systems?

When linear search is OK

Scan each element until match—O(n). Acceptable when data is unsorted, tiny (n < ~50), or only one lookup and sorting cost dominates.

• Linked list without index—must walk nodes.
• Small in-memory config lists, feature flags.
• Hardware / embedded tables where n is bounded.

int linearSearch(int[] a, int x) {
  for (int i = 0; i < a.length; i++) if (a[i] == x) return i;
  return -1;
}