Golang

Given an array slice of integers. Write a function remove that deletes all zeros Examples: remove([]) -> [] remove([0]) -> [] remove([1,0,0,2]) -> [1,2]

Senior

OZON

Hash was calculated, bucket found, new value inserted. What happens when a new value with the same hash (collision) arrives?

Middle+

OZON

What can be done to avoid map evacuation in a high-load service?

Middle+

OZON

Given the "orders" table: +----+---------+---------------------+-------------+ | id | user_id | created_at | price_total | +----+---------+---------------------+-------------+ | 1 | 111 | [phone]:00:00 | 2000 | | 2 | 222 | [phone]:00:00 | 1000 | | 3 | 111 | [phone]:00:00 | 2000 | | 4 | 222 | [phone]:00:00 | 5000 | | 5 | 333 | [phone]:00:00 | 1000 | +----+---------+---------------------+-------------+ Write an SQL query that returns the number of orders for each user with price_total greater than or equal to 1000, sorted in descending order by order count: +---------+-------------+ | user_id | order_count | +---------+-------------+ | 111 | 2 | | 222 | 1 | | 333 | 1 | +---------+-------------+

Middle+

OZON

What will the program output? Why? func main() { timeStart := time.Now() _, _ = <-worker(), <-worker() println(int(time.Since(timeStart).Seconds())) } func worker() chan int { ch := make(chan int) go func() { time.Sleep(3 * time.Second) ch <- 1 }() return ch }

Senior

OZON

Does gRPC operate over HTTP or not? How does it work?

Senior

OZON

What happens in INNER JOIN if one row on the left matches multiple rows on the right?

Middle+

OZON

What does the Index Only Scan vs Index Scan in PostgreSQL depend on?

Middle+

OZON

Imagine a year has passed in the company — what should happen for you to realize you made the right choice?

Senior

OZON

What are your expectations from the company besides the project?

Senior

OZON

Display unique combinations of user and product ID for all purchases made by users before they were banned. Sort first by username, then by SKU. Find users who made purchases totaling more than 5000 rubles. Display their names in the format user ID | first name | last name | total purchases.

Middle

OZON

How was the configuration of ClickHouse set up in shards and replicas?

Senior

OZON

-- Condition -- Find categories where the parent category is the same as the category itself -- Sort the result by id in ascending order -- EXAMPLE -- +----+----------+-----------+ -- | id | name | parent_id | -- +----+----------+-----------+ -- | 1 | pharma | 1 | -- | 2 | products | 4 | -- | 3 | games | 3 | -- | 4 | music | 2 | -- +----+----------+-----------+ -- EXPECTED RESULT -- +--------+ -- | name | -- +--------+ -- | pharma | -- | games | -- +--------+

Senior

OZON

Why did you decide to change jobs and join Ozon?

Middle+

OZON

Have you worked in a company as an external or full-time employee?

Middle

OZON

Implement a function that takes []any and delta int. It should increase only the first occurrences of unique integers by delta. Other types and repeated numbers should remain unchanged. The function should return the updated slice and two numbers: - updated — how many unique numbers were changed, - duplicates — how many numeric elements turned out to be duplicates func IncrementUniqueIntsInMixed(xs []any, delta int) ([]any, int, int) { // your code }.

Middle+

OZON

What are TCP and UDP, and what is the difference?

Middle

OZON

If a high-priority filter is too broad and eats up the entire budget — how to solve it?

Senior

OZON

Briefly about production: who deploys, who monitors, and so on

Senior

OZON

Scenario For example, creating an order. There is a request to the service and a response, and between these two actions, we log the products ordered (for example, to count product popularity). The analytics service periodically runs slowly or times out, and we fail to respond, losing orders. What should be done to stop losing orders and, consequently, money?

Middle+

OZON