Node.js Database Integration 2

Question 1

Which method in the `pg` (node-postgres) library is used to execute a parameterized query safely?

Accepted Answer

client.query('SELECT * WHERE id = $1', [id])

Answer

Parameterized queries use `$1, $2` placeholders with a values array to prevent SQL injection.

Question 2

In Mongoose, what does calling `.lean()` on a query do?

Accepted Answer

Returns plain JavaScript objects instead of Mongoose documents

Answer

`.lean()` skips Mongoose document hydration, returning raw POJOs which are faster and lighter.

Question 3

What is the purpose of connection pooling in Node.js database drivers?

Accepted Answer

To reuse existing connections instead of opening a new one per query

Answer

Connection pooling maintains a set of open connections that can be reused, reducing the overhead of establishing new connections.

Question 4

Which Sequelize method is used to define an association where one User has many Posts?

Accepted Answer

User.hasMany(Post)

Answer

`User.hasMany(Post)` creates a one-to-many association, adding a foreign key to the Posts table.

Question 5

In Redis with the `ioredis` client, which command stores a value with an expiration time of 60 seconds?

Accepted Answer

client.set('key', 'value', 'EX', 60)

Answer

`SET key value EX 60` sets a key with a 60-second expiry; `setex` also works but takes args as `(key, seconds, value)`.

Node.js Practice Test