Java

How to ensure sequential processing of transactions for one user in Kafka?

What is the Outbox pattern and how does it work?

What is LazyInitializationException in Hibernate and how to work with it?

In what order should columns be specified in a composite index? Does the order matter?

/** * Find the person with the minimum age in a room with the maximum number of people * At the end of the solution method, call writeSolution(user, room) */

What are indexes in PostgreSQL? Pros and cons, types of indexes.

- list the names, with the first column showing the name, - the second column showing the number of visitors with that name, - the third column showing the number of visitors with that name and older than 27 years - sort by name in ascending order (A-Z) SQL code example: ```sql create table customers ( id int, name text, age int ); insert into customers values (1, 'John', 20), (2, 'John', 20), (3, 'John', null), (4, 'John', 37), (5, 'Jane', null), (6, 'Bob', 13), (7, 'Bob', 99); SELECT name, COUNT(*) AS total, COUNT(CASE WHEN age > 27 THEN 1 END) AS older_27 FROM customers GROUP BY name ORDER BY name ASC; ```

Tell me about a super complex task you worked on for a long time and eventually solved.

Delivery guarantees in Kafka (at-most-once, at-least-once, exactly-once) and message order

What are optimistic and pessimistic locking? When should each be used?

Tell about transaction isolation levels in PostgreSQL.

Why is it not allowed to make an HTTP request inside a database transaction?

What are partitions in Kafka and how do you choose their number?

The problem of OFFSET pagination on large tables and how to solve it (cursor-based pagination)

How to implement a scenario: save to database, call an HTTP request, enrich data, and save again — transactionally?

Have you used the @Transactional annotation in Hibernate? Tell about working with transactions.