Get interview ready.
Without the noise.
Learn the concepts that matter. Practice what gets asked. Test yourself before the interview.
Aggregation pipeline
$match → $group → $sort → $limit
Filter, group, order, take the top n. The shape most aggregation interview questions actually use.
Try practice problemWhat are you preparing for?
Pick a topic and start with the essentials.
MongoDB
- Learn the essentials
- Practice queries
- Interview questions
- Cheat sheet
Node.js
Coming soon- Learn the essentials
- Practice scenarios
- Interview questions
- Cheat sheet
Redis
Coming soon- Learn the essentials
- Practice scenarios
- Interview questions
- Cheat sheet
SQL
Coming soon- Learn the essentials
- Practice queries
- Interview questions
- Cheat sheet
Docker
Coming soon- Learn the essentials
- Practice scenarios
- Interview questions
- Cheat sheet
AWS
Coming soon- Learn the essentials
- Practice scenarios
- Interview questions
- Cheat sheet
Kafka
Coming soon- Learn the essentials
- Practice scenarios
- Interview questions
- Cheat sheet
System Design
Coming soon- Learn the essentials
- Practice case studies
- Interview questions
- Cheat sheet
Low-Level Design
Coming soon- Learn the essentials
- Practice case studies
- Interview questions
- Cheat sheet
DSA
Coming soon- Learn the essentials
- Practice problems
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- Cheat sheet
See how it works
A lesson, a problem, a question. Same idea for every technology.
MongoDB · Aggregation
$group
Combines documents that share a key. Used for totals, counts, averages, and any “per X” question.
db.orders.aggregate([
{
$group: {
_id: "$customerId",
total: { $sum: "$amount" }
}
}
])- totals
- counts
- averages
- grouping data
Total spending by customer
Ignore cancelled orders, group the rest by customer, and return the top 10 totals.
$group · $sort · $limit
Try problemWhat happens in the Node.js event loop when a Promise and a setTimeout callback are both scheduled?
The Promise runs first. After the current call stack, Node drains the microtask queue — that is where Promise callbacks live — and only then runs timer callbacks from the macrotask queue.
So Promise.then always fires before a setTimeout(..., 0) scheduled in the same turn. Interviewers want that distinction, not the entire event-loop diagram.
Built for the night before the interview.
You don't always need another 20-hour course.
Sometimes you just need to quickly remember how something works, solve a few problems, and make sure you can explain it in an interview.
That's what this is for.
No endless documentation.
No unnecessary theory.
No information overload.
Just: Learn → Practice → Interview