Java

What happens if hashCode() always returns 0? All elements go into one bucket, HashMap expands — will this help?

What do you see as the specifics of high-load systems? How do they differ from medium-load systems in terms of design?

How much data was stored in the database (in KB/GB)?

Where did the figure 35K come from, and how was it calculated?

What solutions would you suggest for a database with a large amount of data, increasing number of consumers, and data volume?

Tell us about the personalized tariff recommendation module — what was the logic behind it, and who made the decision to recommend?

Tell about a project at Gazprom.

How is HashMap structured internally and how does it work?

init: int a = 0 int b = 0 volatile int c = 0 t1: a = 1 b = 2 c = 3 t2: println(c) println(b) println(a)

What is the difference between hashCode() and System.identityHashCode()?

How are elements compared in a red-black tree inside a HashMap if the keys do not implement Comparable?

What indexes do you use in relational databases (PostgreSQL)? How does B-Tree differ from Hash index?

Tell us about the MegaFon project, what did you do?

What principles guided the decomposition of the monolith into microservices? How did you determine which part to isolate into a separate service?

Why did you leave MegaFon?

How did you implement parallel request processing with Kafka? What was the implementation?

Regarding the universal adapter — was there a single protocol for external payment gateways, or is it an abstraction level?

Who planned the tasks for sprints?

Who has worked on developing microservices from scratch to production?