How the stock market, payments and crypto work behind the screen, in plain English, written by engineers who have built and run these systems.
New here? Start with What Happens When You Buy a Stock? How UPI Works How Market Data Reaches Your Screen
Buying shares, IPOs, circuits, market data, and who holds your shares.
In under a second your app says Executed, but the shares arrive the next working day. Here is the whole trip: your broker, the exchange’s order book, the clearing corporation and the depository.
Not your broker. Your shares sit at a depository, in your name. Why the system is split this way, what it means if a broker shuts down, and how to check for yourself.
In India, your shares sit at CDSL or NSDL in your own name. In the US, they’re usually held in your broker’s name, through DTC. What that means, and what happens if a broker fails.
Every price change on your trading app starts at the exchange. How market data travels to your screen, what Level 1, Level 2 and tick-by-tick mean, and why prices can look delayed.
You apply, your money is blocked, and three days later you may or may not get shares. How IPO allotment works in India: the T+3 timeline, the lottery, and checking your status.
Why a stock gets stuck at its upper or lower circuit, how price bands work in India, why they exist, and the market-wide circuit breakers that pause everything.
What happens when you pay by UPI or card, and who earns what along the way.
You scan, enter your PIN, and the shop’s phone pings. Behind it: your app, NPCI and two banks. How a UPI payment works step by step, and why one sometimes gets stuck.
Subscriptions without entering your PIN every month, and small payments in one tap. How UPI AutoPay mandates and UPI Lite work, their limits, and when to use which.
Tap, beep, Approved. In those seconds your card, the shop’s bank, Visa, Mastercard or RuPay and your own bank all take part. How a card payment works, and why one gets declined.
Visa and Mastercard don’t lend you money or set your limit. So where does their money come from? The card fee every shop pays, how it is split, and why UPI is free.
When you pay on a website, a payment gateway sits between the shop and your bank. How it works step by step, gateway vs aggregator, and why “money debited, order not placed” happens.
How bank transfers, cheques and international payments move your money.
Three ways to send money between bank accounts in India. How NEFT, RTGS and IMPS move your money, their limits and charges, and which one to use when.
The paper cheque doesn’t travel any more. How cheque clearing works in India with the Cheque Truncation System, how long it takes now, what banks check, and why cheques bounce.
SWIFT doesn’t move money: it moves messages. How international transfers really work, why they’re slow and expensive, sending money to and from India, and the faster alternatives.
How Bitcoin, stablecoins, tokenized gold, crypto exchanges and crypto loans actually work.
No bank in the middle: your wallet signs, the network checks, a miner records. How a Bitcoin transaction works step by step, why fees change, and what confirmations mean.
Three very different designs all promise “one coin, one dollar”. What holds each one there, and what happened in 2022 and 2023 when two of them slipped.
A stock exchange matches buyers with sellers. A decentralised exchange has no order book at all: a formula sets the price. How that works, and what it costs you on a big trade.
No credit check, no loan officer. You lock up more than you borrow, and code sells it if prices fall too far. How on-chain lending works, and where it breaks.
A token on a blockchain, backed by real gold in a vault. How tokenized gold works, how it compares with app “digital gold” and gold ETFs, and what to check before trusting one.
Code, diagrams and engineering detail: latency, scaling and engineering practice.
In trading, being a few microseconds late means acting on an old price. Where latency comes from, who it hurts, and what exchanges do so that speed doesn’t turn into an unfair advantage.
Blocking sockets, select, epoll, kernel bypass, FPGAs and io_uring: what each one changed in the path from the network card to your code, with C++ sketches and when to use which.
Humans test the happy path. AI-generated suites systematically explore the edges — null inputs, boundary conditions, type coercions — that engineers unconsciously skip because they wrote the code being tested.