Exploring Tech, Finance & Productivity
Practical articles, free developer tools, and finance calculators. No jargon, no fluff.
Design Truecaller (Crowdsourced Caller ID) - System Design
An unknown number rings your phone and, before you pick up, the screen says “Rajesh Kumar - Reported as spam 240 times.” You have never …
Read MoreNSC vs KVP vs Post Office Time Deposit: Which Wins After Tax for a 30 Percent Bracket Investor
Here is the line that gets repeated at every post office counter: “KVP doubles your money, NSC gives you tax benefit, TD gives you …
Read MoreTool-Calling Patterns That Actually Work in Production AI Agents
Most agent tutorials show the same thing: define one tool, let the model call it once, print the result, declare victory. That is not an …
Read MoreCI/CD for AI Applications Is Different - What Changes When Your Logic Lives in a Prompt
A git commit does not capture what your AI application actually does. You can freeze every line of Python, tag the release, and deploy the …
Read MoreDesign a CDN (Content Delivery Network) - System Design
A CDN sounds like a caching proxy you already know how to build: put an Nginx in front of the origin, set a TTL, done. That intuition …
Read MoreDesign a DNS Resolver System - System Design
A DNS resolver sounds like a lookup table: a client asks “what is the IP for example.com,” you return an A record, done. That intuition …
Read MoreDesign Jira (Bug / Issue Tracking) - System Design
Jira looks like a CRUD app with extra menus. Create a ticket, assign it, drag it across a board, close it. Say that in an interview and the …
Read MoreNPS Is Not as Illiquid as You Think: The 25 Percent Partial Withdrawal Rule
The single most common objection to NPS is one word: illiquid. “Your money is locked till 60.” That line kills the product for most people …
Read MoreDesign Coursera / Online Learning Platform - System Design
An online learning platform looks like “YouTube with a login” for about a minute, and then the differences bite. Video is only one plane of …
Read MoreDesign Multiplayer Game Matchmaking - System Design
Everyone thinks matchmaking is “put waiting players in a list, grab the first ten, start a game.” That works in a hackathon demo with fifty …
Read MoreDesign Online Auction (eBay) - System Design
An online auction looks like “a listing with a current price that goes up,” and if you model it that way you will lose the interview in the …
Read MoreSovereign Gold Bond: The Tax Math of Selling Early Versus Waiting 8 Years
Most people think the SGB lock-in is the problem: eight years with your money stuck. That framing is backwards. The eight-year clock is not …
Read MoreTechnical Debt Is a Business Problem - How to Get Your Manager to Care About Refactoring
Your manager does not care that the payment module is “a mess.” They have heard that sentence about six different modules from four …
Read MoreDesign Coinbase (Crypto Exchange) - System Design
“Let users buy and sell crypto” hides two different, both-irreversible problems welded together. Inside the exchange, Coinbase is a matching …
Read MoreDesign Robinhood (Stock Trading Platform) - System Design
“Let a user buy and sell stocks” sounds like a form that writes a row. Then you notice where the money and the shares actually live. …
Read MoreDesign Venmo / P2P Payment - System Design
Venmo looks like a wallet with a Twitter feed bolted on, and that framing is exactly what makes it interesting. The money side demands …
Read MoreNRI Investing in India - The NRE and NRO Account Confusion Finally Explained
Most NRIs I have talked to hold both an NRE and an NRO account, and almost none of them can tell you which money is supposed to go where. …
Read MoreTDS on FD: Does Splitting Across Banks Actually Beat Submitting Form 15G
Here is the uncomfortable truth almost every “how to avoid TDS on FD” article skips: for a taxpayer, avoiding TDS saves exactly zero rupees …
Read MoreDesign GitHub (Code Hosting + PRs) - System Design
“Host code and let people review changes” sounds like a CRUD app with a diff view. It is not. Under the hood you are running a fleet that …
Read MoreDesign LinkedIn (Professional Graph + Feed) - System Design
LinkedIn looks like Twitter with a suit on. It has a feed, it has profiles, people follow each other. So candidates walk in ready to reuse …
Read MoreDeveloper Tools
JSON Formatter
Format, validate & minify JSON instantly in your browser.
Open ToolJWT Decoder
Inspect JWT header, payload, and expiry without sharing tokens.
Open ToolProtobuf Encoder
Encode JSON to Protobuf binary or decode binary back to JSON.
Open ToolRegex Tester
Test regex patterns with real-time matching and group highlights.
Open ToolBase64 Encoder
Encode and decode Base64 strings with a single click.
Open ToolHash Generator
Generate MD5, SHA-1, SHA-256, and SHA-512 hashes instantly.
Open ToolUUID Generator
Generate random v4 UUIDs. Copy with one click.
Open ToolUnix Timestamp
Convert between Unix timestamps and human-readable dates.
Open ToolFinance Calculators
SIP Calculator
Calculate monthly SIP growth with the power of compound interest.
EMI Calculator
Find your EMI for home loans, car loans, or personal loans.
1 Crore SIP
Figure out how much SIP you need to build 1 crore.
Emergency Fund
Calculate exactly how much emergency fund you should have.
HRA Calculator
Compute your tax exemption under Section 10(13A).
Investment Growth
Project your portfolio's future value with annual step-ups.
Want to practice coding? Browse 50 DSA problems with clean solutions.