Exploring Tech, Finance & Productivity
Practical articles, free developer tools, and finance calculators. No jargon, no fluff.
Advance Tax Trap: Why Salaried Employees with Capital Gains or Rent Owe 234B Interest
Your employer deducts TDS on every salary credit, and for most people that is the entire tax story. So the natural assumption is that if you …
Read MoreDesign Password Manager (1Password / LastPass) - System Design
A password manager looks like a trivial CRUD app. Store some login records, sync them across the user’s phone and laptop, auto-fill them …
Read MoreDesign Single Sign-On (SSO / OAuth Provider) - System Design
Single Sign-On sounds like a login screen. It is not. It is a token factory that a hundred applications trust, sitting at the center of an …
Read MoreDesign UPI / PhonePe (Real-Time Payments) - System Design
“Scan a QR, money leaves your HDFC account and lands in a shopkeeper’s SBI account in three seconds” sounds like one API call. It is not. …
Read MoreeBPF Makes Production Debugging Feel Like Cheating - A Practical Intro for App Engineers
The last time a service of mine went slow in production and the dashboards showed nothing, I did what every application engineer does: added …
Read MoreDesign a CAPTCHA Service - System Design
Everyone pictures a CAPTCHA as a picture of squiggly text. “Render some distorted letters, ask the user to type them, check the string, …
Read MoreDesign Reverse Image Search (Google Images) - System Design
Reverse image search looks like a search problem, and it is - but not the kind you get from an inverted index of words. A user hands you a …
Read MoreDesign Shazam (Audio Fingerprinting) - System Design
You hold your phone up to a speaker in a loud cafe, capture five seconds of a song you half-recognize, and a moment later the screen names …
Read MoreKafka Consumer Lag Is Lying to You - How to Measure and Fix It Properly
Every Kafka incident review I have sat in has the same slide near the end: a graph of consumer lag that stayed flat and green for the entire …
Read MoreSenior Couple Parking Rs 90 Lakh: How SCSS and PMVVY Together Beat a Plain FD Ladder
Your parents, both past 60, have ₹90 lakh from a sold flat and a matured LIC endowment sitting in a savings account earning 3%. The banker’s …
Read MoreDesign a Distributed Lock Service (ZooKeeper / etcd) - System Design
There is a small category of infrastructure that is boring on the surface and terrifying underneath: the thing that every other service …
Read MoreDesign Google Translate - System Design
Google Translate looks like a text box: you type “hello,” you get “hola,” done. That intuition survives one short sentence. The moment you …
Read MoreDesign S3 (Object Storage) - System Design
An object store looks like a hash map with two methods: PUT(key, bytes) and GET(key) -> bytes. That framing is exactly why it is hard. A …
Read MoreClickHouse Is Not Just for Big Data - When to Replace PostgreSQL for Analytics
Most teams do not choose ClickHouse. They run away from PostgreSQL until it stops working, panic, and reach for whatever managed analytics …
Read MoreDesign Apple Find My / Google Find My Device - System Design
Find My looks like a location-tracking problem and it is, but the interesting half is a paradox: you must locate a device that is offline - …
Read MoreDesign Snapchat / Instagram Stories - System Design
Stories look like a photo feed with a countdown, and people design them like one. That is the trap. A story is not a permanent post you …
Read MoreDesign Voice Assistant (Alexa) - System Design
You say “Alexa, what’s the weather in Bangalore tomorrow?” and about eight hundred milliseconds later a speaker on your kitchen counter says …
Read MoreYou Can Claim HRA and Home Loan Interest Together: The Dual-City Tax Hack Most Miss
Almost everyone who owns a home loan property believes the HRA in their salary slip is now dead money. “I own a flat, so I can’t claim HRA” …
Read MoreDesign a Spam / Fraud Detection Pipeline - System Design
Everyone thinks fraud detection is a set of if statements. “Block logins from Nigeria, flag transactions over $5000, rate-limit signups per …
Read MoreDesign Gmail (Email Service Backend) - System Design
Email looks like a solved problem. It is 40 years old, the protocol fits on a napkin, and every framework ships a send_mail() in three …
Read MoreDeveloper Tools
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Convert between Unix timestamps and human-readable dates.
Open ToolFinance Calculators
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HRA Calculator
Compute your tax exemption under Section 10(13A).
Investment Growth
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Want to practice coding? Browse 50 DSA problems with clean solutions.