Parottasalna Course Notes

📝 Parottasalna Blog

248 practical articles on backend engineering, system design, databases, Docker, Python, AI and DSA, explained simply.

Latest articleProgramming
Programming

Breaking Big Problems into Small, Reliable Steps with Prompt Chaining

Large Language Models (LLMs) often feel intelligent enough to handle anything in a single instruction. But in real world applications, giving one massive prompt is like asking a human to cook, serve, clean, and manage…

Feb 7, 2026 · 6 min read
Programming Basics

There is nothing Random inside a computer

Have you ever wondered how your music app shuffles thousands of songs, or how a video game generates a brand new world every time you hit “New Game”?…

Feb 7, 2026 · 3 min read
Programming

Django Forms & Validations — From Simple to Advanced

When I first started learning Django, forms looked magical. I would write a few lines, call is_valid() , and Django somehow knew whether my data was …

Feb 5, 2026 · 6 min read
Data Science

MovieLens 360: User Retention, Recommendation & Engagement Analytics

Imagine You are working as a Data Scientist in “StreamFlix” – a Netflix-like platform Management Problems Users install app → watch few movies → disa…

Feb 5, 2026 · 2 min read
E-Commerce Analytics

E-Commerce Customer 360, Churn & Revenue Analytics

1. Business Problem (Industry Scenario) You are hired as a Data Scientist for an online marketplace similar to Amazon/Flipkart. The company has 3 maj…

Feb 5, 2026 · 2 min read
Work Culture

Ahhh... Working From Office again due to AI automations

For the last few years, working from home became a normal part of life, especially in the IT industry (Side effect of Covid). Employees enjoyed flexi…

Jan 8, 2026 · 2 min read
Miscellaneous

Many people accidently typed perplexity.in instead of perplexity.com ?

People often see what they want to see. They hear what they want to hear. And recently, a viral claim has been circulating, Type perplexity.in and se…

Nov 23, 2025 · 1 min read
Prompt Engineering

It seems there are names for "way of asking questions", called as Prompt Engineering

Prompting is the process of giving specific instructions, questions, or examples to a Large Language Model (LLM) like ChatGPT to guide its output tow…

Nov 9, 2025 · 3 min read
Programming

Have you been told "Use plain SQL, its faster than ORM" ?

You might have heard this advice before, Just use SQL; no need for ORMs. At first glance, that sounds elegant. SQL is expressive, close to the metal,…

Nov 9, 2025 · 3 min read
Machine Learning

A performance measurement for machine learning classification problem where output can be two or more classes, simply called as Confusion Matrix

In Machine Learning, the problem of classification involves predicting the categorical class label to which the query data point belongs. And the con…

Nov 8, 2025 · 3 min read
Machine Learning

Saving and Reviving a Basic Machine Learning Model

In Machine learning, while working with the scikit-learn (sklearn) library or any other modules, we need to save the trained models in a file and res…

Nov 8, 2025 · 2 min read
SQL

Introduction to DDL (Data Definition Language) in SQL

When we talk about databases, we usually think of inserting, updating, or deleting data. But before doing any of that, we must first define the struc…

Nov 8, 2025 · 3 min read