Engineering Distributed Systems & Payment Platforms

Staff Software Engineer at PayPal leading core platform teams. 9+ years building high-throughput payment infrastructure, distributed transaction architectures, and next-generation agentic commerce protocols.

View Enterprise Work Side Projects
10,000+ tps Peak Transaction Scale
Billions / Day Financial Volume Guided
Team of 10 Engineers Led at PayPal

Enterprise Engineering at PayPal

Core platform architectures and inventions designed to handle transaction volumes at global scale.

Invention & Patent Pending

Agentic Checkout Protocol

As commerce shifts to autonomous AI agents acting on behalf of users, standard web2 redirect gateways and biometric 2FA prompts fail. I authored a patent disclosure for a headless payment gateway protocol linking cryptographic pub/sub message relays (Nostr NIP-01, NIP-44, NIP-42) to centralized fiat ledgers.

The system leverages ephemeral session keys to prevent merchant invoice spam and implements cryptographic non-repudiation (secp256k1) to eliminate chargeback fraud, unlocking lower interchange fees for AI-driven transactions.

Cryptography Nostr Protocol WebSocket Bus Non-Repudiation JSON Schemas
Zero Chargeback Fraud Risk
Headless 2FA & Redirect Bypass
Platform Architecture

Distributed Transaction Integrity

Led the platform migration and structural redesign of core legacy payment monoliths into modular microservices. Designed high-reliability transaction models using Saga and Transactional Outbox patterns to ensure ledger safety across sharded Postgres databases and high-volume Kafka clusters.

Championed the adoption of at-least-once delivery semantics coupled with mandatory, distributed idempotency validation keys, ensuring zero balance corruption or duplicate charges under network partitions while maintaining low processing latency.

Java Go Kafka PostgreSQL Saga Pattern Idempotency
10k req/s Platform Concurrency
99.999% Availability Target
Data Infrastructure

Real-Time Personalization Engine

Engineered real-time, low-latency backend pipelines for shopping personalization, processing massive checkout telemetry datasets. Implemented caching layers utilizing Redis (cache-aside for hot reads) and high-throughput databases to render custom promotions and fraud signals during active user checkouts.

Go Redis Elasticsearch Distributed Caching
Millions Active Users Serviced
< 15ms Edge Response Latency

Product Portfolio & Open Source

Active side projects focused on local-first engineering, native integrations, and specialized AI agents.

Mobile App

Inkwell Comics

Fully native Android comic, manga, and webtoon reader. Integrates static C `libarchive` binaries via JNI. Highly optimized rendering pipeline maintaining 120 FPS page transitions. Bypasses Android 15 JNI SELinux limitations on Samsung devices via Kotlin ParcelFileDescriptor passing.

Kotlin Compose JNI / NDK libarchive Room
Google Play Source Code
Backend Server

Fructus API

Self-hosted investment portfolio database and server. Integrates directly with Morgan Stanley (E*TRADE) via SnapTrade API. Exposes REST endpoints and an HTTP Model Context Protocol (MCP) server for local AI-driven balance and position audits.

Go SQLite MCP Server SnapTrade
Active Server
AI Agent

ThesisWatch

Autonomous market research agent. Monitors Go-indexed portfolio holdings, reads local markdown investment theses, and evaluates them against live market news utilizing the Gemini API with active Google Search grounding.

Go Gemini SDK Search Grounding Markdown
Agent Daemon
Web App

Nostr Handshake

A database-free digital contract signing SPA. Leverages NIP-44 encrypted payloads and NIP-07 browser extensions to exchange, sign, and cryptographically seal agreements peer-to-peer over a high-concurrency Go relay.

HTML5 / JS Nostr Web Cryptography Go Relay
Source Code
Desktop Integration

Dota 2 GSI

Low-latency companion app tracking real-time match events. Pulls Valve's Game State Integration JSON payloads locally, prompting tactical voice alerts and strategy queues during competitive matches.

PowerShell Valve GSI Electron Windows API
Source Code
Home Server

Pi 5 Personal NAS

NVMe-backed private cloud server. Runs Nextcloud, Tailscale, and automated GnuPG backup engines inside Docker containers to synchronize secure personal data clusters locally.

Raspberry Pi 5 Docker Compose Tailscale Nextcloud
Hardware Build

Architectural Philosophy

The principles, patterns, and trade-offs that guide my design decisions.

Enterprise Systems & Platforms

Convergence Through Primitives

A single clean primitive reused globally outvalues multiple fragile, bespoke paths. I design platform contracts around highly constrained capabilities (scoped on buyer, merchant, and ceiling axes) rather than constructing separate pipelines for each partner.

Strict Boundary Preservation

Trust boundaries are non-negotiable. I enforce a structural split between buyer-present consent capture (Stage 1) and buyer-absent execution (Stage 2), isolating sensitive vault contexts and ensuring system state is never fabricated downstream.

Economic-First System Design

Systems must justify themselves against business loss. I design architectures by modeling transaction margins and chargeback risks—such as replacing legacy redirects with cryptographic non-repudiation (secp256k1) to eliminate transaction fraud.

Falsifiable, Documented Decisions

I run a rigorous, options-first decision ledger listing explicit trade-offs and pros/cons. I value intellectual honesty and maintain a documented "right to reverse" when production telemetry or code audits disprove my prior hypotheses.

Local-First & Native Engineering

Sovereign Data

Users should own their data. I build consumer apps that prioritize local storage (SQLite, Storage Access Framework) and offline-first capabilities. Applications should work seamlessly without cloud lock-in or tracking.

Jank-Free Native Execution

Consistency over convenience. I write native integrations (JNI/NDK, static C libraries) to guarantee sub-millisecond data extraction and 120 FPS UI operations, avoiding the performance penalties of heavy web-wrappers.

Zero-Dependency Core

Every external dependency is a security and maintenance liability. I design database schemas from scratch and write custom implementations for core features, ensuring complete control over the application stack.

The Engineer

Shubham Kokul

I am a Staff Software Engineer at PayPal leading platform teams. For nearly a decade, I have focused on distributed transaction systems, fintech security patterns, API design, and legacy migrations at PayPal.

SolutionByHour is my workspace for shipping software products that challenge standard cloud-bloat paradigms. When I am not designing payment flows or writing Go backends, I am auditing portfolio positions with local AI agents, running Docker on custom Pi clusters, or playing Elden Ring and Dota 2.

Staff Engineering Level
9+ Yrs Fintech Experience
Go / Java Primary Languages