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     - [Incident Management](categories/devops/incident.md)
 - [Web](categories/web.md)
 - [Success Team Work](categories/team-work.md)
+- [Uncategorised](categories/uncategorised.md)
 - English
   - [Business English Speaking for Professionals](categories/english/business-spoken-english.md)
diff --git a/categories/uncategorised.md b/categories/uncategorised.md
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+# Uncategorised
+
+
+## Some interesting questions
+
+### UUID or UUID4
+
+* `UUID` use current time and your computer MAC address to generate the id
+* `UUID4` which is much simpler. Each and every bit of a UUID v4 is generated randomly and with no inherent logic. With the sheer number of possible combinations (2^128), it would be almost impossible to generate a duplicate unless you are generating trillions of IDs every second, for many years.