Oracle PostgreSQL Interview Questions 2026
Published July 22, 2026 · Updated July 22, 2026
5 real PostgreSQL interview questions asked at Oracle. Upvoted by engineers who cleared the loop. Covers Technical, System Design rounds.
5 questions
153 engineers asked
261 upvotes
Company: Oracle
Technology: PostgreSQL
All PostgreSQL Questions Asked at Oracle
Oracle
Medium
Technical round
PostgreSQLMySQL
Explain Oracle's MVCC (Multi-Version Concurrency Control) and how it enables consistent reads without blocking writers.
How does it differ from SQL Server's locking approach? What are the downsides of MVCC (undo log growth, long-running transactions)?
↑ 88 upvotes · 33 engineers asked this · SDE2
Oracle
Hard
System Design round
Distributed SystemsPostgreSQL
Design a distributed SQL database that supports ACID transactions across shards.
Explain two-phase commit (2PC), its failure modes, and how Google Spanner uses TrueTime to replace 2PC with a more scalable approach.
↑ 41 upvotes · 39 engineers asked this · SDE2
Oracle
Hard
Technical round
PostgreSQLMySQLJava
Explain Oracle's redo log and undo log. How do they work together to provide crash recovery and read consistency? Walk through what happens when a transaction commits, then the server crashes, then restarts.
↑ 51 upvotes · 31 engineers asked this · SDE2
Oracle
Medium
Technical round
PostgreSQLMySQL
Write a SQL query to find the Nth highest salary from an Employee table without using LIMIT/TOP. Then solve it with a window function (DENSE_RANK) and explain which is more portable across Oracle, PostgreSQL, and MySQL.
↑ 63 upvotes · 42 engineers asked this · SDE1
Oracle
Medium
Technical round
3-6 yearsPostgreSQL
What is the difference between a PostgreSQL VIEW and a MATERIALIZED VIEW? When would a materialized view actually hurt you?
↑ 18 upvotes · 8 engineers asked this · Senior SDE
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Frequently asked questions
Explain Oracle's MVCC (Multi-Version Concurrency Control) and how it enables consistent reads without blocking writers.
Explain Oracle's MVCC (Multi-Version Concurrency Control) and how it enables consistent reads without blocking writers.
How does it differ from SQL Server's locking approach? What are the downsides of MVCC (undo log growth, long-running transactions)?
Design a distributed SQL database that supports ACID transactions across shards.
Design a distributed SQL database that supports ACID transactions across shards.
Explain two-phase commit (2PC), its failure modes, and how Google Spanner uses TrueTime to replace 2PC with a more scalable approach.
Explain Oracle's redo log and undo log. How do they work together to provide crash recovery and read consistency? Walk through what happens when a transaction commits, then the server crashes, then restarts.
Explain Oracle's redo log and undo log. How do they work together to provide crash recovery and read consistency? Walk through what happens when a transaction commits, then the server crashes, then restarts.
Write a SQL query to find the Nth highest salary from an Employee table without using LIMIT/TOP. Then solve it with a window function (DENSE_RANK) and explain which is more portable across Oracle, PostgreSQL, and MySQL.
Write a SQL query to find the Nth highest salary from an Employee table without using LIMIT/TOP. Then solve it with a window function (DENSE_RANK) and explain which is more portable across Oracle, PostgreSQL, and MySQL.
What is the difference between a PostgreSQL VIEW and a MATERIALIZED VIEW? When would a materialized view actually hurt you?
What is the difference between a PostgreSQL VIEW and a MATERIALIZED VIEW? When would a materialized view actually hurt you?