# card Published articles for card. This is one page of public article previews, not the complete archive. Follow Next page to continue. Summaries are not the original full articles. ## Built for Reliability: How American Express Processes Payments at Scale DevFeed: [Built for Reliability: How American Express Processes Payments at Scale]() Original publisher: [Read original article]() Author: ByteByteGo Published: 2026-09-08T18:31:03Z Content type: article Language: en Sources: [ByteByteGo]() Topics: [Architecture & Design](), [Microservice](), [Microservices](), [Network](), [Server]() Tags: [account-balance](), [architecture](), [bank](), [card](), [cell-based-architecture](), [microservices](), [network](), [payments](), [scale](), [server](), [services]() ### AI overview The article explains how American Express processes payments through a cell-based architecture. Transactions move through independent processing units and microservices, with isolation designed to limit disruption when services fail. ### Source excerpt In this article, we will try to understand how the transaction runs through such a cell-based architecture and how the payments are processed even when some services are failing. ## Security Week 2632: массовый угон криптовалюты у пользователей кошельков COLDCARD DevFeed: [Security Week 2632: массовый угон криптовалюты у пользователей кошельков COLDCARD]() Original publisher: [Read original article]() Author: Kaspersky\_Lab ("Лаборатория Касперского") Published: 2026-08-04T03:26:05Z Content type: news Language: ru Sources: ["Лаборатория Касперского" RU]() Topics: [Security](), [Randomizer]() Tags: [card](), [coin](), [kite](), [research](), [security](), [tag-9fe8963de219](), [tag-d14eb265d33e](), [tag-d4be1d74f775]() ### AI overview A predictable software random-number implementation in COLDCARD hardware wallets allowed an attacker to reconstruct wallet seeds and steal cryptocurrency. By August 1, reports cited 1,367 stolen bitcoins from 4,585 addresses, worth approximately $88 million. ### Source excerpt Громкой новостью прошлой недели стала массовая кража криптовалюты у пользователей холодных кошельков COLDCARD. Хотя в теории холодные кошельки (аппаратные устройства, хранящие данные для доступа к криптовалюте) лучше защищены от кибератак, но в реальности COLDCARD подвела ошибка при реализации криптографического алгоритма: вместо надежной аппаратной генерации случайных чисел использовалась программная реализация, результаты работы которой могли быть предсказаны. Злоумышленник смог реконструировать так называемый сид, открывающий доступ ко всем сохраненным на кошельках секретам, для большого количества кошельков,. Правильность вычисления сида могла быть проконтролирована путем сверки с публичными данными, включая историю транзакций в биткоинах. Имея на руках всю необходимую информацию, организатору атаки оставалось перевести средства на собственные кошельки. Точно оценить итоговый ущерб пока затруднительно, но по данным на 1 августа было украдено 1367 биткоинов с 4585 адресов, это примерно соответствует 88 миллионам долларов. Читать далее ## B2B Virtual Card Payments: A Seller's Guide DevFeed: [B2B Virtual Card Payments: A Seller's Guide]() Original publisher: [Read original article]() Author: Aarthi Poonia Published: 2026-07-30T00:00:00Z Content type: tutorial Language: en Sources: [Dodo Payments Blog]() Topics: [Finance](), [Software as a service]() Tags: [ach](), [b2b](), [card](), [fees](), [guide](), [payments]() ### AI overview A seller-focused guide to B2B virtual card payments. It explains how buyer AP teams issue supplier-locked or single-use card numbers for specific invoices, compares virtual cards with ACH, wire transfers, and checks, and describes seller costs, controls, and reconciliation concerns. ### Source excerpt How B2B virtual card payments work, why buyers' AP teams prefer them, what they cost you as the seller, and how to reconcile them without manual keying. ## How Razorpay Built a Customer Data Platform for Queryable Segments at Scale DevFeed: [How Razorpay Built a Customer Data Platform for Queryable Segments at Scale]() Original publisher: [Read original article]() Author: Varun Meka Published: 2026-06-26T08:06:33Z Content type: article Language: en Sources: [Razorpay Engineering - Medium]() Topics: [data](), [Transactions](), [App](), [systems](), [Apache Spark]() Tags: [app](), [banking](), [card](), [customer](), [data](), [devices](), [engineering](), [payments](), [platform](), [razorpay](), [saas](), [scale](), [shopping](), [transactions]() ### AI overview Razorpay describes building an in-house Customer Data Platform to unify fragmented customer and transaction data into queryable audience segments. The supplied excerpt says the platform serves segments across more than 500 million user profiles in under 30 milliseconds while keeping personally identifiable information isolated in source systems. ### Source excerpt Turning Scattered Data Into Queryable Segments at Scale: How Razorpay Built Its Customer Data Platform A consent-native CDP that serves audience segments across 500M+ user profiles in under 30ms, with PII isolated to the source systems. The Problem We Were Solving A customer opens her favourite online shopping app, adds a few items to her cart, and pays INR 1,200 via UPI, powered invisibly by Razorpay. A week later she returns and pays using a saved Visa card from her laptop. Later that month, she places a larger INR 8,500 order through net banking from work. Three transactions. Three different payment instruments. Three different devices. To the merchant's engineering team, and to Razorpay's data systems, these could look like three completely different people, unless you've done the hard work of figuring out they're all the same customer. Now suppose this is a D2C fashion brand approaching their Diwali sale. The merchant's growth team has a clear plan: "Identify customers who have transacted at least once in the last 30 days, have spent more than INR 5,000 cumulatively this quarter, and haven't enrolled in our loyalty programme. Send them an early-access nudge with a personalized discount 48 hours before the public sale opens." A year ago, answering that question at Razorpay meant filing a cross-team data request, waiting for an analyst to write a custom Spark job, and getting an answer in 2-3 days. By the time the merchant had the segment, the Diwali sale was already live. The early-access window had closed. The campaign got sent to a broader, less-targeted audience, wasting spend on customers who would have bought anyway and leaving cold customers untouched. Now multiply that pain by millions of merchants. Razorpay powers payments and growth for over 12 million merchants. From D2C fashion brands and SaaS startups to subscription platforms, ed-tech companies, and the 2 million+ local merchants accepting QR payments every day. Together, they process billions of transaction ## Plaid vs Stripe: Why They Solve Different Problems (Not Competitors) DevFeed: [Plaid vs Stripe: Why They Solve Different Problems (Not Competitors)]() Original publisher: [Read original article]() Author: Ayush Agarwal Published: 2026-06-11T00:00:00Z Content type: tutorial Language: en Sources: [Dodo Payments Blog]() Topics: [stripe](), [App](), [data]() Tags: [ach](), [bank-transfers](), [banking](), [card](), [comparisons](), [developer-tools](), [fintech](), [integration](), [payments](), [stripe]() ### AI overview This guide compares Plaid and Stripe, explaining that Plaid connects bank accounts and provides account data and verification, while Stripe primarily processes card payments and offers related financial products. It identifies ACH transfers as their main area of overlap and explains how the platforms can be used together. ### Source excerpt Plaid vs Stripe compared. Why they are not really competitors, where each one fits, and how they can be used together for ACH, banking, and card payments. ## Raw Card APIs and PCI Compliance: A SaaS Reality Check DevFeed: [Raw Card APIs and PCI Compliance: A SaaS Reality Check]() Original publisher: [Read original article]() Author: Ayush Agarwal Published: 2026-05-16T00:00:00Z Content type: article Language: en Sources: [Dodo Payments Blog]() Topics: [Software as a service](), [Security](), [API]() Tags: [apis](), [card](), [checkout](), [compliance](), [payment](), [saas](), [scope](), [security]() ### AI overview This article explains how raw card APIs give SaaS products greater control over payment flows while significantly expanding PCI compliance scope, engineering responsibilities, and audit costs. It compares raw card handling with hosted or embedded payment forms and identifies integration scenarios where the trade-off may be justified. ### Source excerpt Raw card APIs give you full control over the payment form but expand PCI scope dramatically. When the trade off makes sense and when it absolutely does not. ## Indian Payment Methods for Global SaaS: UPI, Cards, NetBanking, Wallets DevFeed: [Indian Payment Methods for Global SaaS: UPI, Cards, NetBanking, Wallets]() Original publisher: [Read original article]() Author: Ayush Agarwal Published: 2026-05-13T00:00:00Z Content type: tutorial Language: en Sources: [Dodo Payments Blog]() Topics: [Software as a service](), [Transactions]() Tags: [billing](), [card](), [checkout](), [cross-border-payments](), [guide](), [india](), [integration](), [payment](), [payments](), [saas](), [subscriptions]() ### AI overview A guide to accepting payments in India for global SaaS, covering UPI, Indian-issued cards, NetBanking, wallets, RBI subscription mandates, recurring-payment delays, and integration considerations. ### Source excerpt How global SaaS accept UPI and Indian-issued cards, the RBI mandate rules for subscriptions, the 48-hour processing delay, and integration patterns that win in India. ## Accept Payments in Africa: A Complete Guide for SaaS Companies DevFeed: [Accept Payments in Africa: A Complete Guide for SaaS Companies]() Original publisher: [Read original article]() Author: Ayush Agarwal Published: 2026-04-05T00:00:00Z Content type: tutorial Language: en Sources: [Dodo Payments Blog]() Topics: [Software as a service](), [Localization (l10n)](), [Transactions]() Tags: [africa](), [bank-transfers](), [card](), [compliance](), [digital-wallet](), [global-expansion](), [guide](), [merchant-of-record](), [mobile](), [payments](), [saas](), [transactions]() ### AI overview This guide explains how SaaS and digital product businesses can accept payments across Africa. It emphasizes mobile money, local bank rails, transfers, USSD, and localized payment methods over card-only checkout, and discusses currencies, compliance, and Merchant of Record services. ### Source excerpt How to accept payments across Africa with the right payment methods, currencies, and compliance setup for SaaS and digital product businesses. ## Best Payment Gateway for SaaS 2026: Stripe vs Paddle vs PayPal vs 5 More DevFeed: [Best Payment Gateway for SaaS 2026: Stripe vs Paddle vs PayPal vs 5 More]() Original publisher: [Read original article]() Author: Ayush Agarwal Published: 2026-03-10T00:00:00Z Content type: comparison Language: en Sources: [Dodo Payments Blog]() Topics: [Software as a service](), [stripe](), [SDKs](), [.env]() Tags: [2026](), [alternatives](), [api](), [billing](), [card](), [comparison](), [compliance](), [cross-border](), [developer](), [fees](), [global](), [merchant-of-record](), [payment](), [payment-gateway](), [payments](), [paypal](), [pricing](), [saas](), [stripe](), [subscription](), [vs]() ### AI overview A comparison of payment gateways for SaaS businesses in 2026, covering transaction fees, international payments, tax compliance, subscription billing, payment recovery, dispute handling, and Merchant of Record versus payment service provider models. It also presents Dodo Payments as a unified option for global SaaS operations. ### Source excerpt Honest 2026 SaaS payment gateway comparison: real fees, MoR vs PSP, country coverage, dispute handling, and which one fits indie hackers, mid-market, and global SaaS. ## How to Accept Online Payments on Your Website in 2026 DevFeed: [How to Accept Online Payments on Your Website in 2026]() Original publisher: [Read original article]() Author: Ayush Agarwal Published: 2026-03-09T00:00:00Z Content type: tutorial Language: en Sources: [Dodo Payments Blog]() Topics: [Software as a service](), [Website](), [Security](), [tokenization]() Tags: [2026](), [ach](), [authentication](), [authorization](), [b2b](), [card](), [chargebacks](), [checkout](), [compliance](), [data](), [engineering](), [fees](), [fraud](), [fraud-prevention](), [gateway](), [global](), [guide](), [how-to](), [merchant-of-record](), [payments](), [saas](), [tax]() ### AI overview A practical guide for SaaS teams, indie founders, and digital product companies on accepting online payments in 2026. It explains payment flows, gateways, processors, merchant accounts, tokenization, 3D Secure, PCI DSS, taxes, fraud prevention, chargebacks, and region-specific payment methods. ### Source excerpt Learn how to accept online payments in 2026 with the right stack for global tax, local methods, checkout flows, and Merchant of Record coverage. ## Best Payment Methods for SaaS in 2026 DevFeed: [Best Payment Methods for SaaS in 2026]() Original publisher: [Read original article]() Author: Joshua D'Costa Published: 2026-01-13T00:00:00Z Content type: article Language: en Sources: [Dodo Payments Blog]() Topics: [Software as a service](), [Mobile]() Tags: [2026](), [apple](), [bank](), [card](), [checkout](), [compliance](), [conversion](), [ecommerce](), [google](), [mobile](), [payment](), [payments](), [saas](), [subscriptions](), [tokenization]() ### AI overview This article reviews major payment methods for SaaS businesses in 2026, including cards, digital wallets, buy now, pay later, cryptocurrency, and cash on delivery. It explains how the methods work and outlines their advantages and drawbacks, including fees, settlement delays, PCI compliance, and chargeback risk. ### Source excerpt See the top payment methods SaaS customers prefer in 2026 with pros, cons, regional coverage, and selection tips to improve checkout conversion rates. ## NCMC design and technical limitations DevFeed: [NCMC design and technical limitations]() Original publisher: [Read original article]() Published: 2026-01-03T18:46:00Z Content type: opinion Language: en Sources: [Personal blog of Anurag Bhatia]() Topics: [Internet](), [Transactions](), [Risk](), [systems]() Tags: [card](), [dmrc](), [internet](), [ncmc](), [npci](), [payment-systems](), [payments]() ### AI overview The article examines India's National Common Mobility Card (NCMC), focusing on its offline-wallet design and how it differs from online UPI and card payments used in other transit systems. ### Source excerpt I was in Mumbai a few months ago for the Equinix India Peering forum. The event happened to be very near the airport & I found that the airport, conference venue, hotel, and a few other locations I was visiting were all near the newly built Mumbai Line 3 (Aqua Line). To save on hassle with regular tickets, I went for an NCMC (National Common Mobility Card). Most people travelling in the Delhi metro would be aware of it by now, thanks to a bit of marketing push inside the metro train with announcements. Mumbai line 3 has a tie-up with SBI for the card, and thus, I got the SBI card. Ended up using it in Mumbai, Delhi and Chennai over the last few months. Lately, I have been reading about way NCMC works, the limitations of the Indian NCMC design compared to other mass transit systems. In many countries, mass transit systems simply use MasterCard/Visa/Apple Pay tap and charge directly from the respective card (credit/debit card, etc.), like the London tube, Stockholm metro, HK airport express, Singapore, etc. Indian deployment is bit different. Indian NCMC offline wallet concept The whole idea of NCMC is to have a single card which can make payment for public transport, including metro, buses etc across the country digitally. It has to be fast and reliable, and this is where the whole tech differs from systems like UPI or Visa/MasterCard/Rupay POS payments. In case of UPI as well as credit/debit card payments on POS machines - entire transaction runs online. Money goes from the person paying the amount to the receiver as part of a settlement facilitated by NPCI. I don't need to go in detailed steps involved there, but the key idea is that there's an active involvement of 1) Payer's APP 2) Payer's bank 3) Receiver's PSP 4) Receiver's bank 5) NPCI UPI switch, etc. All these have to work and most important - internet has to work. 😀 All this largely works well for casual payments across the vendors, but not for transit payments, especially at metro stations. It easily takes ## UPI Autopay: Benefits and Use cases DevFeed: [UPI Autopay: Benefits and Use cases]() Original publisher: [Read original article]() Author: Joshua D'Costa Published: 2025-11-21T00:00:00Z Content type: tutorial Language: en Sources: [Dodo Payments Blog]() Topics: [Software as a service]() Tags: [automatic](), [bank](), [billing](), [card](), [india](), [payments](), [product](), [saas](), [scheduled](), [subscriptions](), [webhooks]() ### AI overview This tutorial explains UPI Autopay for SaaS and subscription businesses serving customers in India. It covers mandate creation and approval, scheduled or variable automatic debits, merchant setup, and notifications through webhooks. ### Source excerpt Understand UPI Autopay for SaaS subscriptions in India, including mandate flows, merchant setup steps, user benefits, and renewal success impact. ## Get started with Firebase using Free Trial credits DevFeed: [Get started with Firebase using Free Trial credits]() Original publisher: [Read original article]() Author: Andrew Peynado; Rachel Saunders Published: 2024-11-04T00:00:00Z Content type: tutorial Language: en Sources: [Firebase Blog]() Topics: [Firebase](), [Cloud](), [Google](), [Google Cloud Platform (GCP)](), [App](), [Development]() Tags: [billing](), [card](), [cloud](), [console](), [develop](), [firebase](), [free](), [full-stack-development](), [google-cloud](), [guide](), [how-to](), [onboarding](), [pricing](), [tutorials](), [upgrade]() ### AI overview This tutorial explains how to claim $300 in Google Cloud Free Trial credits and link the billing account to a Firebase project. The credits last 90 days, require a payment method for billing setup and identity verification, and do not incur charges unless the account is upgraded to a paid account. ### Source excerpt News, tutorials, and updates from the Firebase team. ## Storing customer card information securely using Point of Sale API. DevFeed: [Storing customer card information securely using Point of Sale API.]() Original publisher: [Read original article]() Author: Tristan Sokol Published: 2017-12-13T21:15:24Z Content type: tutorial Language: en Sources: [Square Corner Blog RSS Feed]() Topics: [API](), [App]() Tags: [api](), [apis](), [card](), [code](), [customer](), [payment]() ### AI overview This tutorial explains how to use Square's Point of Sale API to save a customer's payment card to a profile through the Square Point of Sale app, then charge the stored card through the Transaction or Charge API for future billing and subscriptions. ### Source excerpt You can use Square's Point of Sale API to save payment information to a customer profile directly from the Square Point of Sale app. Once a card is stored, you can use the Transaction API to charge this card in the future, unlocking fast remote billing an ## Connection goes down, business stays up DevFeed: [Connection goes down, business stays up]() Original publisher: [Read original article]() Author: Square Engineering Published: 2014-05-06T16:06:00Z Content type: article Language: en Sources: [Square Corner Blog RSS Feed]() Topics: [Mobile](), [Security](), [iOS](), [Network]() Tags: [app](), [card](), [data](), [engineering](), [fetch](), [information](), [infrastructure](), [internet](), [ios](), [mobile](), [network](), [offline](), [privacy](), [private-key](), [public-key](), [security](), [server]() ### AI overview Square's Offline Mode lets mobile sellers continue accepting credit card payments during temporary cell or Wi-Fi outages. Payment data is encrypted on the seller's device, uploaded in batches when connectivity returns, and cleared after server receipt; sellers have 72 hours to reconnect. ### Source excerpt Introducing Offline Mode ## The Odds of Finding a Set in The Card Game SET DevFeed: [The Odds of Finding a Set in The Card Game SET]() Original publisher: [Read original article]() Published: 2010-04-28T00:00:00Z Content type: article Language: en Sources: [Peter Norvig]() Topics: [math](), [Simulation]() Tags: [card](), [color](), [game](), [number](), [results](), [set](), [simulation]() ### AI overview An analysis of why the odds of finding no SET in the card game SET change during play. A simulation shows that the chances differ substantially between a freshly dealt layout and layouts reached after SETs are repeatedly removed and replaced, suggesting the instruction booklet's odds do not describe the course of an actual game. ### Source excerpt Correcting an error in the instruction booklet for the card game SET ## How CVV, CVV2, and CVC Values Are Calculated DevFeed: [How CVV, CVV2, and CVC Values Are Calculated]() Original publisher: [Read original article]() Author: Graham King Published: 2005-10-23T16:46:27Z Content type: article Language: en Sources: [Graham King]() Topics: [Algorithm](), [des](), [account](), [Network]() Tags: [account](), [algorithm](), [bank](), [batch](), [card](), [concatenation](), [credit-card](), [des](), [format](), [network](), [numbers](), [parameter](), [payment](), [value](), [verification]() ### AI overview This article explains that CVV, CVV2, CVC, and Indent CVC are three-digit card verification values calculated with the same CVV algorithm. It describes the inputs, including the card number, expiration date, service code, and DES keys, and explains variations involving card batches, service codes, and expiration-date formats. ### Source excerpt Unraveling the mysteries of card verification values.