Identifiers need uniqueness within a defined scope. Ordering, unpredictability and compactness are separate properties.
Before you start
You should understand API requests, storage and basic capacity estimates. Begin with a concrete user action and its correctness requirement. Draw data flow and failure boundaries before selecting infrastructure; a technology name by itself does not explain why a design meets the requirement.
The practical goal is to reason through this situation: A distributed ID can be unique without accurately recording business-event order. Read the walkthrough first, then try the interview exercise before opening its answer. The important part is explaining the decision and its consequences, rather than remembering a definition alone.
Step-by-step walkthrough
Step 1: Separate desired properties
Uniqueness, ordering and unpredictability are different requirements.
Step 2: Choose generation scope
Distributed generation must fit collision and operational assumptions.
Step 3: Keep authorization independent
An ID’s obscurity or format is not an access decision.
Worked scenario
A distributed ID can be unique without accurately recording business-event order.
An unpredictable resource ID makes enumeration harder but still requires ownership checks. A time-oriented distributed ID may improve some ordering or index behavior without representing precise business-event chronology. Store the actual event time when needed and explain the identifier’s guarantee under clock or generator failure.
Common mistake
Treating an ID as proof of permission creates an access vulnerability.
Verify the behavior
Test generation boundaries and unauthorized access regardless of identifier knowledge.
Interview exercise
Choose IDs for public resources.
Answer and reasoning
Balance generation, indexing and information exposure, and enforce authorization independently of identifier knowledge.
Continue learning
Compare the scenario with the System Design interview questions and test your understanding with the System Design MCQs. For terminology and implementation details, consult the reference material.