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I'm Soundar, a Senior Software Engineer with 12+ years designing and delivering secure, high-scale distributed systems and payments platforms for global leaders like Slack, Amazon, and Microsoft. I focus on reliability, security, and scalable integration with third-party gateways, delivering value through thoughtful architecture, pragmatic delivery, and collaborative leadership. I enjoy solving onboarding, API design, and international expansion challenges, leading cross-functional teams to ship fast while maintaining a strong customer focus. I’m passionate about mentoring engineers, improving CI/CD and security posture, and turning complex problems into clear, actionable solutions.…I'm Soundar, a Senior Software Engineer with 12+ years designing and delivering secure, high-scale distributed systems and payments platforms for global leaders like Slack, Amazon, and Microsoft. I focus on reliability, security, and scalable integration with third-party gateways, delivering value through thoughtful architecture, pragmatic delivery, and collaborative leadership. I enjoy solving onboarding, API design, and international expansion challenges, leading cross-functional teams to ship fast while maintaining a strong customer focus. I’m passionate about mentoring engineers, improving CI/CD and security posture, and turning complex problems into clear, actionable solutions.

Soundar Vellingiri

Full Stack Developer, Back-End Developer, Web Developer, +2

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I'm Soundar, a Senior Software Engineer with 12+ years designing and delivering secure, high-scale distributed systems and payments platforms for global leaders like Slack, Amazon, and Microsoft. I focus on reliability, security, and scalable integration with third-party gateways, delivering value through thoughtful architecture, pragmatic delivery, and collaborative leadership. I enjoy solving onboarding, API design, and international expansion challenges, leading cross-functional teams to ship fast while maintaining a strong customer focus. I’m passionate about mentoring engineers, improving CI/CD and security posture, and turning complex problems into clear, actionable solutions.…I'm Soundar, a Senior Software Engineer with 12+ years designing and delivering secure, high-scale distributed systems and payments platforms for global leaders like Slack, Amazon, and Microsoft. I focus on reliability, security, and scalable integration with third-party gateways, delivering value through thoughtful architecture, pragmatic delivery, and collaborative leadership. I enjoy solving onboarding, API design, and international expansion challenges, leading cross-functional teams to ship fast while maintaining a strong customer focus. I’m passionate about mentoring engineers, improving CI/CD and security posture, and turning complex problems into clear, actionable solutions.

Available to hire

I’m Soundar, a Senior Software Engineer with 12+ years designing and delivering secure, high-scale distributed systems and payments platforms for global leaders like Slack, Amazon, and Microsoft. I focus on reliability, security, and scalable integration with third-party gateways, delivering value through thoughtful architecture, pragmatic delivery, and collaborative leadership.

I enjoy solving onboarding, API design, and international expansion challenges, leading cross-functional teams to ship fast while maintaining a strong customer focus. I’m passionate about mentoring engineers, improving CI/CD and security posture, and turning complex problems into clear, actionable solutions.

Skills

Experience Level

Expert

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Intermediate

Language

English

Fluent

Work Experience

Senior Software Engineer at Slack

October 1, 2022 - Present

Growth Engineering (Sign-in & Onboarding): Designed and executed a rigorous onboarding road map with 20+ A/B tests, optimizing the onboarding funnel and driving improvements in user retention and free-to-paid conversion. AI‑driven Onboarding: Led the development of a personalized onboarding engine that automatically provisions teams, channels, and configurations based on user intent, reducing time-to-value for new organizations. Infrastructure Reliability: Implemented improvements for critical Sign-in and Onboarding APIs, boosting service level objectives and reducing latency for millions of daily active users. Multi-tenant Payment Gateway: Architected a sandboxed payment gateway framework using Groovy, enabling runtime control and rapid integration of third‑party gateways (e.g., Stripe). Global Expansion & Ops: Implemented gateway-driven capabilities to launch Mobile Carrier Billing in Japan and led end-to-end accounting integration for the Amazon.nl marketplace. Operational Excel

Senior Software Engineer II at Amazon

April 1, 2018 - October 1, 2022

Healthcare Payments (Amazon Care): Led the payments infrastructure launch for Amazon’s healthcare business. Designed a HIPAA‑compliant anonymous payment processing backend to securely de-identify sensitive patient health data from Amazon’s core financial systems. Revenue & Platform: Engineered a dynamic checkout/payment preference engine that reduced click friction, contributing to $350M+ in annual revenue uplift. System Architecture: Built a multi-tenant, sandboxed payments gateway framework in Groovy to enable runtime control and rapid integration of third‑party gateways (e.g., Stripe). Global Expansion: Drove Mobile Carrier Billing in Japan and end-to-end accounting integration for Amazon.nl; enabled global expansion with compliant financial flows. Operational Excellence & Leadership: Accelerated new marketplace launches by virtualization of fulfillment constraints and helped hire 10+ engineers.

Software Engineer at Microsoft

October 1, 2015 - April 1, 2018

Platform & APIs for Dynamics 365: Architected platform components to expose critical APIs enabling third‑party developers to build apps on top of the Dynamics CRM platform. High‑throughput payments workflows & data integrity: Implemented secure, scalable payment processing with a focus on reliability in a multi-tenant cloud environment. Collaboration & Delivery: Partnered with product and engineering teams across regions to deliver robust services on tight timelines.

Software Engineer II / Web Team Lead at Groupon

April 1, 2013 - September 1, 2015

Migration & Modernization: Led APAC Web Team in migrating legacy Rails/Java platforms to Node.js, significantly improving performance and developer velocity. Security & Conversion: Built a bot verification and email validation service to filter malicious traffic and optimize confirmation workflows, boosting user conversions. Internationalization: Re-engineered core modules for i18n and launched a responsive deal-view homepage for Malaysia and Singapore. Marketing Tech: Created a REST-based marketing campaign tool to dynamically serve personalized offers to users.

Senior Software Engineer at LACK

October 1, 2022 - Present

Growth Engineering: Designed and executed onboarding roadmap with 20+ A/B tests, optimizing onboarding funnel and boosting freemium-to-paid conversions. AI-Driven Onboarding: Led development of a personalized AI onboarding engine that auto-provisions teams, channels, and configurations based on user intent, dramatically reducing time-to-value. Infrastructure Reliability: Architected improvements to critical Sign-in and Onboarding APIs, enhancing SLAs and reducing latency for millions of daily active users.

Web Team Lead / Software Engineer II at Groupon

April 1, 2013 - September 1, 2015

Migration & Modernization: Led the APAC Web Team in migrating legacy Rails/Java platforms to Node.js, significantly improving performance and developer velocity. Security & Conversion: Bot verification and email validation service that filtered malicious traffic and streamlined confirmations. Internationalization (i18n): Re-engineered core modules to support internationalization and launched a responsive deal-view homepage for Malaysia and Singapore. Marketing Tech: Built a REST-based marketing campaign tool to dynamically serve personalized offers based on location and history.