Best of Fintech — 2025

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   Article

   Groww Engineering·27w

   When Two Databases Become One: How DuckDB Saved Our Trading Operations from Manual Reconciliation

   A trading platform faced recurring position-order mismatches across two separate MySQL databases, requiring 20-30 minutes of manual reconciliation by two engineers. By leveraging DuckDB's MySQL scanner extension to perform cross-database joins, they automated the entire process into a 2-3 minute operation running every 15 minutes. The solution eliminated manual intervention, improved accuracy from 85% to 99.9%, and enabled proactive monitoring instead of reactive fixes during market hours.

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   UX Planet·41w

   I Opened My Credit Card App While on a Call, & This UX Surprised Me

   Robinhood's credit card app demonstrates excellent context-aware UX design by showing a security warning only when users are on phone calls. The bright yellow banner warns users that Robinhood isn't calling them, helping prevent phone scams. This just-in-time design approach is more effective than constant warnings because it appears exactly when the risk is highest, avoiding alert fatigue while building user trust through thoughtful security communication.

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   UX Planet·25w

   How India’s Largest Payment App Fixed a Problem with Just a Plus Button

   Paytm solved a common friction point in payment flows by adding a plus button directly to the amount entry screen, eliminating the need to switch between apps for calculations. The case study demonstrates how identifying micro-frictions in user behavior and addressing them with minimal interface changes can significantly improve user experience. The article explores potential extensions of this concept and emphasizes the importance of observing where users pause or break their workflow.

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   The PayEng Playbook·1y

   5 Common Antipatterns in Payment Systems Design

   Good payment engineers focus on business logic rather than performance or clean code. Common antipatterns in payment system designs include relying solely on synchronous responses from PSPs, confusing payments with money transfers, building on a card-first design, using incorrect state machines, and sticking to early database decisions. Addressing these issues can lead to more robust and maintainable payment systems.

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   Article

   Product Hunt·28w

   Logo.dev: Reliable logos for any product, instantly.

   Logo.dev is an API service that provides reliable brand logos for companies, stock tickers, and crypto symbols through simple URL-based fetching. Built as a replacement for Clearbit's discontinued logo API, it offers global CDN delivery, automatic fallback logos, daily updates, and serves over a billion requests monthly to 25,000 developers. The service is free for most users and designed to be a stable, long-term solution for displaying logos in dashboards, SaaS products, and internal tools.

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   Article

   ByteByteGo·1y

   How AMEX Processes Millions of Daily Transactions With Millisecond Latency

   American Express processes millions of transactions daily with millisecond latency by overhauling its payment system in 2018. Moving from legacy infrastructure to a modern cloud-ready system improved scalability, flexibility, and security. The key component, Global Transaction Router (GTR), uses Go language for concurrency, gRPC over HTTP/2 for faster internal communication, and asynchronous logging for performance optimization. Profiling, benchmarking, reader-writer mutexes, and avoiding excessive Go channels are some strategies employed to maintain high transaction processing speed and low latency.

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   Article

   controversy.dev·47w

   Is being over-employed unethical or just efficient?

   A software engineer is being sued for allegedly working multiple full-time jobs simultaneously without disclosure, raising questions about employment ethics in the remote work era. The case highlights the evolving nature of knowledge work and whether traditional employment expectations still apply in an async, AI-powered workplace.

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   Article

   selfhosted·44w

   PersonalAccounter , Simple Self-Hoster Personal/Small-Corporate Accounting Software

   PersonalAccounter is a PHP-based self-hosted accounting management system designed for personal and small corporate use. It offers expense tracking, subscription management, and reporting capabilities with easy deployment and user-friendly interface.

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   SingleStore·1y

   MySQL vs PostgreSQL vs SingleStore Performance in Docker

   The post compares MySQL, PostgreSQL, and SingleStore using a benchmark with over 100 million transactions in Docker containers. The results show SingleStore has superior performance in handling complex queries involving heavy joins and analytics, while MySQL struggles and PostgreSQL performs better than MySQL but not as well as SingleStore. A full benchmarking setup is shared for readers to try on their own systems.

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    Article

    All Things Distributed·30w

    What is USSD (and who cares)?

    USSD, a 30-year-old messaging protocol requiring only 2G connectivity, powers hundreds of billions in financial transactions across Sub-Saharan Africa through companies like M-Pesa and Moniepoint. Behind simple menu-driven interfaces on feature phones, these platforms run sophisticated cloud architectures with ML-powered fraud detection and IoT systems. The technology demonstrates how builders solve real customer problems by choosing suitable tools over shiny ones, creating profitable businesses while serving communities with limited internet access and smartphone penetration.

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    Video

    EO·1y

    How I Built a $300M Startup with No Degree and No NetworkㅣSelfbook, Khalid Meniri

    Khalid Meniri, co-founder and CEO of Selfbook, shares his journey from Algeria to New York City, highlighting his perseverance despite lacking formal education or a professional network. Selfbook revolutionizes the hotel booking industry by integrating digital payment solutions like Apple Pay and streamlining the booking process. Meniri emphasizes the importance of consistent vision, belief in the product, and the necessity of adaptability in overcoming industry challenges.

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    Article

    Groww Engineering·33w

    Building 915: Inside Groww’s High-Performance Trading Terminal

    Groww Engineering built 915.Trade, a high-performance web-based trading terminal for professional traders. The platform features a modular architecture with real-time data streaming using binary messaging, Zustand for optimized state management, and React Compiler for automatic optimization. Key features include direct chart trading, dynamic option chains with live Greeks, a unique straddle chart for volatility tracking, and a scalper widget with keyboard shortcuts. The system uses an EventBus with BroadcastChannel API for widget linking across tabs, enabling traders to create synchronized, shareable workspace layouts.

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    The Verge·41w

    Terraform co-founder Do Kwon pleads guilty over $40 billion crypto collapse

    Do Kwon, co-founder of Terraform Labs, pleaded guilty to conspiracy and wire fraud charges related to the 2022 collapse of Terra stablecoin and Luna token that wiped out $40 billion in investor funds. Kwon admitted to knowingly defrauding customers and artificially inflating Terra's $1 peg. He faces up to 25 years in prison with sentencing scheduled for December 11th, following his extradition from Montenegro to the US.

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    Article

    Medium·47w

    1 Lakh Users. 20K Requests/sec. CQRS & SAGA Patterns Saved Our LMS

    A fintech team faced system failures when their loan management system couldn't handle partial failures during loan rescheduling operations. The monolithic approach caused data inconsistencies when services failed mid-process. They solved this by implementing CQRS to separate read and write operations, and SAGA pattern to manage distributed transactions with automatic rollback capabilities. The solution transformed their system from handling 1 lakh users with frequent failures to processing 20K requests per second reliably.

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    Video

    Awesome·27w

    The complete disappearance of a tech billionaire...

    Jack Ma, founder of Alibaba and China's richest man, saw his empire crumble after a 2020 speech criticizing Chinese regulators and state banks. The government canceled Ant Group's $37 billion IPO, fined Alibaba $2.8 billion, and Ma disappeared for three months. Upon returning, he stepped down from leadership roles and lost half his fortune ($36 billion). The incident demonstrates how China's government maintains control over tech billionaires, regardless of their wealth or global influence.

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    LogRocket·1y

    Fintech UX design: What the best finance apps get right

    Fintech apps like Revolut, Stripe, PayPal, and Wise excel by prioritizing user experience through intuitive onboarding, robust security measures, and user engagement strategies. Their effective use of progressive disclosure, gamification, and customizable interfaces ensures ease of use, boosts confidence, and maintains high user retention. These design principles are essential for simplifying complex financial tasks and building trust in digital finance solutions.

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    Medium·30w

    Create a Stock Screener with MCP Servers in Minutes

    Learn how to build a stock screener using Financial Modeling Prep's MCP Server and the Model Context Protocol. The tutorial demonstrates fetching structured financial data through a unified interface, filtering stocks based on metrics like P/E ratio and debt-to-equity, and implementing the screener in Python with pandas. Setup involves either using Cursor IDE or running a local Docker container, with the MCP server providing clean JSON responses without managing multiple API endpoints or authentication.

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    The PayEng Playbook·36w

    How To Review Code That Deals With Money

    A systematic 4-step approach to reviewing code in financial systems: start with test files to understand context, verify alignment with issue requirements, mentally solve the problem yourself, then compare the actual implementation against your approach. This method helps catch errors early, provides deeper understanding, and is especially critical for payment systems where mistakes can be costly.

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    Groww Engineering·43w

    Making a Real-Time Stock Screener in Groww

    Groww built a real-time stock screener handling 2+ million writes per minute using a single 4-core MySQL instance. The system uses in-memory aggregation to reduce database writes, CDN-based hash caching to handle 50K reads per minute, and a custom query language for extensible filtering. Key optimizations include buffering tick data in memory, selective persistence of minute-level aggregates, and 30-second CDN caching that reduced backend load by 80%. The modular architecture powers multiple screener types and enables rapid feature development.

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    SitePoint·47w

    5 Best Payment Gateways for SaaS: Your Ultimate Guide — SitePoint

    A comprehensive comparison of five payment gateways specifically designed for SaaS businesses: NOWPayments, Authorize.Net, NMI, BridgePay, and CyberSource. The guide covers technical considerations for developers including API quality, SDK availability, webhook support, and PCI compliance features. Each gateway is evaluated based on fees, supported currencies, and developer-friendly features like sandbox environments and client-side tokenization. The article emphasizes the importance of choosing payment solutions that support recurring billing, multiple payment methods, and seamless integration for subscription-based business models.

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    Fullstack Empire·48w

    Get 30+ FREE 3D Fintech wallet illustrations

    A collection of 30+ free 3D fintech wallet illustrations is available for download, featuring wallets, coins, QR codes, and payment scenes without faces. The assets are designed for mobile app UI, mockups, and fintech presentations, accessible through a Figma design file.

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    Community Picks·50w

    TauricResearch/TradingAgents: TradingAgents: Multi-Agents LLM Financial Trading Framework

    TradingAgents is an open-source multi-agent framework that uses specialized LLM-powered agents to simulate real-world trading firms. The system includes analyst teams (fundamentals, sentiment, news, technical), researcher teams for debate-based decision making, trader agents, and risk management components. Built with LangGraph and designed for research purposes, it requires OpenAI and FinnHub APIs and offers both CLI and Python package interfaces for testing trading strategies.

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    ByteByteGo·44w

    How Nubank Uses AI Models to Analyze Transaction Data for 100M Users

    Nubank processes transaction data from 100 million users using transformer-based foundation models instead of traditional manual feature engineering. Their system converts raw transactions into tokenized sequences, trains models using self-supervised learning on trillions of transactions, and combines sequential embeddings with tabular data through joint fusion architecture. The centralized AI platform allows teams across the company to access pretrained models for various financial tasks like credit scoring, fraud detection, and personalization.

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    TechCrunch·1y

    Read the email Jack Dorsey sent when he cut 931 of Block’s staff

    Block, a fintech company, laid off 931 employees, as announced in an email by co-founder and CEO Jack Dorsey. The layoffs were attributed to strategic shifts and performance issues, not financial targets or AI replacements. The cuts were categorized into strategy reasons, performance ratings, and managerial positions, aiming to flatten the company’s hierarchy. Additionally, Block closed nearly 748 open roles, except for certain critical positions. This marks the second significant layoff by Block in 15 months, affecting around 20% of its workforce overall.

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    Hiten Shah·25w

    How a gambling startup is outsmarting the government (for now)

    Kalshi operates as a federally regulated prediction market platform processing $1B monthly by exploiting a legal loophole that classifies event contracts as commodities rather than gambling. The platform charges transaction fees (1-3.5%) instead of taking house odds, enabling users to trade yes/no contracts on events. Technical arbitrage opportunities exist through automated scripts that exploit streaming delays. After securing CFTC approval in 2020 and winning a lawsuit to enable political betting, the platform expanded into sports markets, creating regulatory tensions with states losing tax revenue.

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