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Practical articles, free developer tools, and finance calculators. No jargon, no fluff.
Design IRCTC Train Booking (Tatkal) - System Design
“Book a train ticket” sounds like inserting a row. Then you look at Tatkal. At 10:00:00 sharp, a few days’ worth of demand for a scarce …
Read MoreDesign MakeMyTrip Travel Search - System Design
“Design MakeMyTrip” sounds like a shopping app: a user types two cities and a date, a list of flights comes back, they pick one and pay. The …
Read MoreSenior Citizen Savings Scheme vs FD vs RBI Floating Rate Bond: Post-Tax at 60
You retired last month with ₹40 lakh you want to keep safe and income-producing. Every relative has an opinion: “SCSS, 8.2%, …
Read MoreDesign an Authentication & Login System - System Design
“Let users log in” is the request that hides an entire distributed system. You need to store a password without ever storing the password, …
Read MoreDesign Facebook Marketplace - System Design
Facebook Marketplace looks like “Craigslist with photos,” and if you design it that way you will fail the interview. The naive read is a …
Read MoreDesign Live Stock Prices Worldwide (Bloomberg) - System Design
“Show live prices for every stock on every exchange to millions of people at once” reads like a websocket that pushes a number. Then you …
Read MoreHUF for Tax Saving: Real Numbers for a Rs 20 Lakh Salary Household
Most salaried Indians treat their family as a single taxpayer. It does not have to be. If you are Hindu, Jain, Sikh, or Buddhist, the law …
Read MoreThe Outbox Pattern Is the Only Safe Way to Publish Events After a Database Write
The most dangerous line of code in a microservice is not the one that crashes. It is this one: order = db.save(order) # write to Postgres …
Read MoreDesign Cluster Health Monitoring - System Design
“Monitor the health of the cluster” sounds like a cron job that pings every box and pages someone when one goes quiet. Then you put 50,000 …
Read MoreDesign On-Call Escalation (PagerDuty) - System Design
Everyone thinks PagerDuty is a glorified SMS sender. “A monitoring tool posts an alert, you look up who is on call, and you text them. If …
Read MoreDesign P2P File Transfer (BitTorrent) - System Design
The whole point of a file-transfer service sounds like a solved problem: put the file on a server, hand out a URL, let people download. That …
Read MoreLong Context Windows Do Not Replace RAG - They Change When You Use It
Every few months someone declares RAG dead. The argument is always the same: context windows keep growing, so just stuff the whole corpus …
Read MorePPF Deposit Timing: The April 1-5 Rule That Costs You Real Money
Two people open a PPF account on the same day, put in the same ₹1.5 lakh every year for 15 years, and earn the same 7.1% rate. One ends up …
Read MoreClaude Code in a Team Setting - The Conventions Nobody Writes Down
One engineer using Claude Code is a productivity story. Ten engineers using Claude Code on the same repo, with no shared conventions, is a …
Read MoreDesign Facebook Likes with Live Updates (Including Celebrities) - System Design
Tapping “Like” is the smallest interaction Facebook has. It is one bit: you either like a post or you do not. It looks like a toggle on a …
Read MoreDesign Live Comments on Facebook - System Design
Live comments look like a solved problem until you put a number on it. A celebrity goes live, a million people are watching, and comments …
Read MoreDesign Live Page Viewer Count (Booking.com) - System Design
“23 people are looking at this hotel right now.” It is one line of text, a soft nudge that the room might not be here tomorrow. It looks …
Read MoreSukanya Samriddhi Yojana vs Mutual Fund: The CAGR a Fund Needs to Win
The usual advice for a girl child’s corpus is a one-liner: “equity always beats a government scheme over 21 years, so run an SIP.” It sounds …
Read MoreDesign a Wire Transfer API - System Design
A wire transfer looks like the wallet transfer’s twin, and interviewers love it because it is not. In a wallet, “move 500 from Alice to Bob” …
Read MoreDesign Distributed Tracing (Jaeger / Dapper) - System Design
One request hits your API gateway, which calls auth, which calls the user service, which calls three downstream services, two of which hit a …
Read MoreDeveloper Tools
JSON Formatter
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Encode JSON to Protobuf binary or decode binary back to JSON.
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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
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Compute your tax exemption under Section 10(13A).
Investment Growth
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