void singleChar() { assertEquals("a", }
Middle+
232
Java
14621
265
For example, creating an order. There is a request to the service and a response, with inter-service and external goods described (for example, for calculating the popularity of goods). The service repeatedly performs slowly or times out, and we fail to respond, losing the order. What to do to stop losing orders and, accordingly, money?
Senior
201
Write an SQL query to select the names of the three most read authors currently (those with the most books on hand).
Senior
187
Evaluate the algorithmic complexity of the palindrome problem solution in terms of time and memory. If the alphabet is fixed (English letters, 26 characters), what is the memory complexity?
Senior
178
For an array of numbers arr and a number k, return a new array whose number of repeated elements does not exceed k. Example: Input: arr=[1,1,1,2,3,3,3,4,4], k=3 Output: res=[1,3,4]
Senior
166
Describe the library model. There are 3 entities: "Author", "Book", "Reader". Physically, there is only one book and it can only be with one reader. Create tables for the library considering this.
Senior
158
/** * Implement transferring funds between two accounts. Note that this is a production solution * Input parameters: * @param fromAccountId the unique identifier of the user transferring funds * @param toAccountId the unique identifier of the user receiving funds * @param amount the transfer amount. A positive number */ public void transferMoney(Long fromAccountId, Long toAccountId, BigDecimal amount) { }
Middle+
151
What is VACUUM in PostgreSQL and why is it needed?
Senior
147
Write an SQL query: select the titles of all books with more than three authors.
Senior
146
/** * chars = ['a', 'a', 'a', 'b', 'b', 'c', 'a'] * return: a3b2ca2 */ class JavaTask3Solution { public String compress(char[] chars) { } }
Middle+
145
How to scale a service with linear load growth? What to do when horizontal scaling hits database limits?
Senior
140
Outbox pattern: how to ensure atomicity of database write and event sending to the queue?
Senior
134
How to implement rate limiting for an external API with RPS restrictions? How do virtual threads/coroutines differ from system threads?
Senior
129
Write an SQL query: select the titles of all books currently checked out by readers.
Senior
129
Scenario: There are 3 entities - user, chat, message - User has a name and registration date - Chat has a name and creation date - Message has text, author, and creation date - A user can be part of multiple chats simultaneously - A message must belong to a chat, and cannot belong to more than one chat at the same time - Describe the domain model in the form of tables
Senior
128
What types of sharding exist? Describe the main approaches.
Senior
127
What is the difference between Cassandra and PostgreSQL? Please describe the main differences.
Senior
125
For a given string, it is necessary to determine the length of the largest palindrome that can be formed from its characters. A palindrome is a word that reads the same from the beginning and the end, for example "level" or "deified". Example: Input: aaabbbcccddd Output: 11 (palindrome dccbbaaabbccd)
Senior
119
There are 3 entities - user, chat, message - User has a name and registration date - Chat has a name and creation date - Message has text, author, and creation date - User can be in multiple chats simultaneously - Message must belong to a chat, and cannot belong to more than one chat at the same time - Describe the domain in the form of tables.
Senior
118
Is it necessary to wrap the transferMoney method in @Transactional and why?
Middle+
116