Cognizant Interview Process 2026 — Rounds, Tips & Questions
6 real Cognizant interview questions reported by engineers, with difficulty and round context.
Real Questions Asked at Cognizant
What is the difference between cache() and persist() in Spark? When should you use StorageLevel.MEMORY_AND_DISK?
Write a query to find, for each department, the employee with the second-highest salary, using window functions instead of a correlated subquery.
Explain the difference between INNER JOIN, LEFT JOIN, and FULL OUTER JOIN with a simple example of Orders and Customers tables.
A SELECT query filtering on a non-indexed column takes 8 seconds on a 10 million row table. Would adding an index always help? What's the trade-off of adding too many indexes?
What problem does database normalization (1NF, 2NF, 3NF) actually solve? Give an example of an update anomaly in an unnormalized table.
How would you find out why a specific SQL query is slow before making any changes to it?
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