Tell me about replication in PostgreSQL: master-slave, what happens when a replica fails?
Senior
202
Kotlin
139
0
Tell me about database sharding.
Senior
202
// book(seat_id, user_id) PostgreSQL Begin Transaction(read_commited) seat = select * from seats where id = seat_id for update if(seat == null seat.status == "booked") rollback return error("Seat isnt available") insert into bookings (user_id, seat_id, status, created_at) values (used_id, ...) update seats set status = 'booked' where id = seat_id commit return success()
Senior
200
Do you know what Service Mesh is in Kubernetes?
Senior
199
Why is the closing bracket the key in the Map, and the opening bracket the value? What will change if you do the opposite? What is the complexity of containsValue vs get by key?
Senior
190
Tell me about transaction isolation levels
Senior
163
How does the Dirty Checking mechanism work in Hibernate?
Senior
161
Have Kafka transactions (exactly-once semantics) been used?
Senior
159
How to control load on handles (rate limiting)?
Senior
158
What does VACUUM do in PostgreSQL and why do dead tuples appear?
Senior
157
Why can the Postgres query optimizer use Seq Scan in production but Index Scan in dev/ft with the same indexes?
Senior
156
Tell about partitioning in PostgreSQL.
Senior
156
/*Given a string, implement a function to check the correctness of bracket notation. Each opening bracket must have a corresponding closing bracket. Opening and closing brackets must be in the correct order. Types of brackets: "{", "}", "(", ")", "[", "]". Input: "([]){}[(()())()]" Result: true Input: "[(])" Result: false Because brackets 2 and 3 are incorrect, the closing ']' appears before the closing '('.*/ public boolean check(String s){ Deque<Character> stack = new ArrayDeque<>(); Map<Character, Character> map = Map.of( ')', '(', ']', '[', '}', '{' ); // ((( for( char c : s.toCharArray()){ if(map.containsValue(c)){ stack.push(c); } else if(map.containsKey(c)){ if( stack.isEmpty() || stack.pop() != map.get(c)){ return false; } } } return stack.isEmpty(); }
Senior
156
Tell about optimistic and pessimistic locking, when to apply them?
Senior
154
/* SELECT left.K, left.V1, right.V2 FROM left JOIN right ON left.K = right.K; */ public <K extends Comparable<K>, V1, V2> List<Triple<K, V1, V2>> join(List<Pair<K, V1>> left, List<Pair<K, V2>> right) { return null; } private static class Pair<A, B> { private A first; private B second; Pair(A first, B second) { this.first = first; this.second = second; } } private static class Triple<A, B, C> { private A first; private B second; private C third; Triple(A first, B second, C third) { this.first = first; this.second = second; this.third = third; } }
Senior
151
Tell me about yourself and your work experience
Senior
150
Tell about monitoring and metrics in the project (Prometheus, Grafana)
Senior
150
How to solve the problem of concurrent updates of one entity from two Kafka topics (one topic overwrites changes from the other)?
Senior
143
What was the load on the services? What optimizations were applied?
Senior
131