Node.js

Aggregate functions (SUM, COUNT, etc.) — where can they be used in an SQL query? What is the difference between WHERE and HAVING when using aggregate functions?

Deploying code, the database is fine, the processor is not loaded, but requests via REST API are executed sequentially as if one after another. What could be wrong with the database connection configuration?

var i = 1; i < 5; i++ ) { setTimeout( () => console.log(i), 1000 ); } const userName = new MyComparatorConstructor('Sinichkin'); try { if (userName == "Ivanov" || prev == "Skidorov") { console.log('Access granted'); } else { console.log('Forbidden'); } } catch (error) { if (error instanceof ComparisonProhibited) { } } .valueOf() .toString() String.toPrimitive

TypeScript: what are Omit and Pick? What is the difference between union and intersection types? What will happen if an intersection type is passed to Omit?

Is it possible to hang Node.js on the JavaScript/V8 side without using an infinite while(true) loop? How to make sure the promise queue never empties?

What happened to the database? Migrations have been applied. The database is in a modified state — how to understand what happened and how to recover?

You are deploying a new feature to the test environment and it causes the test environment to go down. What will you do?

You found out through EXPLAIN ANALYZE that your queries are suboptimal. What are the most common causes of query inefficiency?

Please tell about relational databases in general. They include Postgres, I will specify its specifics.

function fixed (f) { const me = this return function next (...a) { if (a.length < f.length) { return function (...b) { return next(...a, ...b) } } return f.call(me, ...a) } } export default fixed

What is an abstract class? What happens if a developer writes ts-ignore and does not implement the abstract class methods?

Microservices: how to implement distributed transactions across multiple microservices with rollback capability? What are Saga and Outbox patterns?

How do you understand asynchrony in Node.js? What are the microtask queue and macrotask queue?

Is Node.js single-threaded or not? How many threads can a Node.js executable file occupy and why? What is libuv and how is it related to the event loop?

JSONB has a binary format. What does this specifically allow to do for a column?

How do JSON and JSONB differ in PostgreSQL?

var i = 1; i < 5; i++ { setTimeout(() => console.log(i), 1000) } const userName = new MyComparatorConstructor('Sinichkin') try { if (userName == "Ivanov" || pet row || Skidorov) { console.log('Access granted') } else { console.log('Forbidden') } } catch (error) { if (error instanceof ComparisonProhibited) { } } .valueOf .toString .String.toPrimitive

What is the difference between interface and type in TypeScript? Why are interfaces needed if there are types and vice versa?

We rolled back the migration, everything is alive. We need to deploy a feature — what will you do next if you just deploy again, and everything will repeat?

Have you encountered problems when normalizing or denormalizing data? How does normalization help with heavy loads on the DBMS?