Arun Castromin Lawrance

Solutions Architect | Enterprise Architect | Product Owner | Technology Consulting

01.

The Backstory

Arun

Hey there! Here's my story

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Sr. Solution Architect & TOGAF Certified Enterprise Architect with 17+ years delivering technology-enabled solutions in core banking, payments, and digital transformation. I've implemented Finacle core banking across India, Middle East, Africa, and APAC for Tier-1 banks including Bank of America, Emirates NBD, and Standard Bank. Currently a key contributor to Application Platform Engineering, delivering RTP solutions and support for global commercial banking in Singapore. With an architect's mindset, I design and build end-to-end solutions — and practise that approach through AI-assisted personal projects in full-stack development, applying architecture thinking from concept to deployment.

17+
Years Experience
5
Regions Served
15K+
Man-days Led
100%
On-time Delivery

Demonstrated Leadership

Mentored and driven cross-functional teams for Tier-1 banking clients with 100% on-time delivery across 15,000+ man-days of deliverables

Business Analyst Acumen

Bridged business and technology — translating complex requirements including regulatory into actionable solutions, driving client onboarding workflows and compliance frameworks

Solutions Architect

Designed and implemented scalable, high-performance banking solutions — from real-time payment systems to regulatory reporting frameworks across global markets

Innovation Mindset

Pioneered unconventional solutions — from self-learning Java to deliver a critical banking module in 2 months, to integrating AI workflows for operational efficiency

02.

Professional Experience

Career Journey

17+ years of enterprise solutioning across 5 countries

Career
Personal
Faith
2020 — Present Sr. Technology Architect
Bank of America (Jakarta, Singapore)
Infosys Ltd.
Driving RTP implementations and NFR delivery for APAC region. Leading architecture decisions for real-time payment systems serving millions of transactions.
5x volumes-ready 60% time reduction
Java Spring Boot Kafka Oracle AWS
2025 Personal
AI-Assisted Learning Journey
New co-pilot unlocked. Building apps with Claude, learning at 10x speed.
2024 Personal
Professional Fitness Journey
From sedentary to shredded. Now coaching others to escape the dad-bod zone.
2021 Personal
Princess Thiya Arrived
New project manager arrived - zero experience, maximum authority.
Feb — Apr 2019 Project Manager
Cholamandalam Finance (India)
Latitude Fintech
Led all-India go-live of loan origination system. Managed end-to-end delivery across all branches with significant reduction in client onboarding time.
All-India go-live ⅔ onboarding reduction
LOS Fintech Agile
2019 Personal
Transition Period
Career focus during brief consulting stint.
2016 — 2019 Entrepreneurial Sabbatical
Creative & Business Ventures
Independent
Explored creative pursuits and business ventures. Wedding photography, short filmmaking, and entrepreneurial experiments.
1st Place — South Indian Film Festival
Photography Filmmaking Business
2016-19 Creative
Exploring Passions
Took a leap to pursue filmmaking, photography, and entrepreneurial ventures.
2016 Achievement
Best Short Film Award
Traded code for cameras. Script to screen - Winner of South India Film fest, against 20+ shortlisted teams.
2012 — 2016 Technology Architect & PM
Standard Bank (South Africa & Nigeria)
EdgeVerve Systems
Led large-scale banking platform implementations. Managed 3000+ man-days of delivery with 100% on-time record. Client's most preferred project manager.
3000+ man-days 100% on-time CMMI Level 4
Finacle Core Banking Oracle
2014 Personal
Tied the Knot
Plot twist: Found the co-star of my life story. The sequel's been amazing.
2008 — 2012 Team Lead & Project Manager
Emirates NBD (Dubai, UAE)
Infosys Ltd.
Led core banking transformation for one of the largest banks in the Middle East. Progressed from developer to team lead to project manager.
6000+ man-days 100% on-time
Finacle Java PL/SQL
2008-2012 Personal
Career Focus Period
Deep dive into international banking projects.
2004 — 2008 Software Developer
Multiple Banks (India)
Infosys Ltd.
Built foundation in enterprise software development across banking domain. Core banking customizations and integrations for Bank Sohar, SBI Overseas, Bank of Alexandria, Bank of India.
Java SQL Core Banking
2004 Faith
Walking with Christ
Found the source of truth. The commit that changed everything.
03.

Certifications & Credentials

TOGAF 9 Certified
The Open Group · Enterprise Architecture
Certified Scrum Product Owner (CSPO)
Scrum Alliance · Agile Methodology
IBM Data Science Professional
IBM · Python, ML, Data Analytics
ISO 31000 Risk Manager
PECB · Risk Management Framework
04.

Skills & Expertise

Competency Overview

Solution Architecture Expert | 17+ years
Core Banking (Finacle) Expert
Data Science IBM Certified
Python Expert
Java Advanced
PL/SQL Expert
Data Analytics (Tableau) Advanced
Agentic AI Implementation Active Practitioner
05.

Domain Expertise

Banking and financial services sub-domains I've architected for, with depth of involvement.

Depth:
Led Architecture
Delivered
Contributed
Awareness
Core Banking
Delivered
Finacle implementations across 3 continents. Account management, transaction processing, GL, and customer information systems. Multi-country regulatory adaptations.
12+ years • 4 major implementations
Real-Time Payments
Led Architecture
RTP/instant payment systems, ISO 20022 messaging, cross-border settlement, event-driven processing.
5+ years • APAC region
Loan Origination
Delivered
End-to-end LOS with automated credit scoring, KYC verification, multi-stage approval workflows. All-India rollout.
NBFC nationwide deployment
NFR & Performance
Led Architecture
Non-functional requirements delivery: load testing at 5x, latency optimization, resilience patterns, capacity planning.
Current focus area
Digital Channels
Contributed
Internet banking, mobile banking integration layers, API gateway design, omni-channel architecture.
Integration architecture
Data Migration
Delivered
Legacy-to-modern platform migrations with parallel-run validation, zero-data-loss guarantees, and reconciliation frameworks.
Multi-country migrations
Risk & Compliance
Contributed
Regulatory reporting architecture, audit logging, data encryption design, PCI-DSS compliance patterns.
Across all implementations
Trade Finance
Awareness
Letters of credit, trade document processing, cross-border trade workflows. Exposure through core banking integrations.
Indirect exposure
Open Banking & APIs
Awareness
PSD2, API gateway patterns, third-party integrations, consent management architecture.
Growing interest
06.

Innovation Lab

Where enterprise architecture meets personal curiosity — I bring the same design rigour from banking systems (scalable patterns, clean separation, testable modules) to personal products, exploring new tech stacks with AI-assisted development and a disciplined 9-step delivery workflow.

castroarun
@castroarun
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Commits
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Repos
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PRs
0
Stars
Last 16 weeks
Less
More
All (12)
Live (8)
Crafting (2)
Concept (2)
Click any card to flip

PRIMMO Building

AI-powered personal strength coach

Communicates via WhatsApp and Voice calls. Uses workout data from REPPIT for personalized training.

Next.js Voice AI Supabase
Click to flip
PRIMMO Architecture

PRIMMO

Building

AI-powered personal strength coach with WhatsApp & Voice AI integration.

9-Step Workflow 2/9 Complete

REPPIT Live

Fitness strength tracking app

Track workouts with real-time timer, progressive overload tracking, and exercise history analytics.

Next.js TypeScript Supabase Capacitor
Click to flip
REPPIT App Screenshots

REPPIT

Live

Fitness strength tracking with real-time timer and progressive overload analytics.

9-Step Workflow 8/9 Complete

NoteApp Live

Privacy-first note-taking app

Offline-first with cloud sync, voice-to-text input, and 200+ automated test cases.

Next.js TypeScript TipTap
Click to flip
NoteApp Screenshot

NoteApp

Live

Offline-first note-taking with cloud sync, voice input, and 200+ test cases.

9-Step Workflow 9/9 Complete

Cinder Spotify

AI-assisted original music

AI-assisted original music project live on Spotify & Apple Music.

Music Production AI/ML
Click to flip
Cinder

Cinder

Spotify

AI-assisted original music project live on Spotify & Apple Music.

Concept to Live Complete

The Little Red Dot Spotify

AI-assisted original music

AI-assisted original music project live on Spotify & Apple Music.

Music Production AI/ML
Click to flip
The Little Red Dot

The Little Red Dot

Spotify

AI-assisted original music project live on Spotify & Apple Music.

Concept to Live Complete

Klarity Live

Developer task board with 15-stage pipeline

Task board with 15-stage pipeline, ETag-based distributed sync, and multi-agent orchestration.

Vite React TypeScript Zustand Tauri
Click to flip
Klarity

Klarity

Live

Developer task board with 15-stage pipeline and distributed sync.

9-Step Workflow 8/9 Complete

Orbit Live

Phone companion for Klarity

Mobile companion with zero-server architecture using GitHub as backend and SHA-based conflict resolution.

React Native Tauri GitHub API
Click to flip
Orbit

Orbit

Live

Phone companion for Klarity with cross-platform sync.

9-Step Workflow 8/9 Complete

Digital Resume Live

Interactive portfolio & resume

AI chat assistant, skills radar, and 9-step workflow showcase.

HTML CSS JavaScript Chart.js
Click to flip
Digital Resume

Digital Resume

Live

Interactive digital resume with AI chat, skills radar, and 9-step workflow showcase.

9-Step Workflow 9/9 Complete

AnyCalc Live

Calculate anything, anywhere

19 interlinked calculators with Plan mode — chain EMI, splits, compound interest, and currency conversions together.

Next.js TypeScript Supabase Zustand
Click to flip
AnyCalc Screenshot

AnyCalc

Live

19 interlinked financial calculators with Plan mode for chained calculations.

9-Step Workflow 9/9 Complete

Portfolio Optimization Crafting

Automated portfolio management

Automate portfolio construction and maintenance to outperform market indexes. Covered calls, rebalancing, and risk analytics.

Python Pandas Kite API
Click to flip

Portfolio Optimization

Crafting

Automated portfolio construction and maintenance to outperform market indexes.

9-Step Workflow 1/9 Complete

Health Reports Tracker Concept

Medical reports organized over time

OCR-powered lab report scanning with historical trend graphs, smart alerts, and doctor-ready summaries for Indian lab formats.

Next.js TypeScript Claude AI Supabase
Click to flip

Health Reports Tracker

Concept

Scan lab reports with OCR, track health parameters across years, and share doctor-ready summaries.

9-Step Workflow 0/9 Complete

Payment House Concept

Enterprise payment processing

Kafka-driven microservices for core banking payments across 4 regions with event sourcing, compliance screening, and clearing house adapters.

Java 21 Spring Boot Kafka PostgreSQL
Click to flip

Payment House

Concept

Kafka-driven, event-sourced microservices for core banking payments across Singapore, Hong Kong, UK, and India.

9-Step Workflow 1/9 Complete
07.

Architecture in Action

Personal projects where I apply enterprise architecture patterns to real products — shipped end-to-end, from design to production.

Why this matters: Enterprise architects design systems. These projects are testimonials that I design, architect, build, ship, and maintain products I own from zero to production.
REPPIT Shipped

Fitness strength tracking app with offline-first architecture and progression state machines.

State Machine Local-First Data Isolation
Next.js TypeScript Supabase Capacitor
User Input
State Machine
(Beginner→Elite)
Supabase
(Cloud + Local)
Multi-Profile
Isolation
Architecture Insight
State machine pattern drives progression through deterministic levels (Beginner → Intermediate → Advanced → Elite) — the same pattern that governs credit tier transitions and KYC status workflows in banking systems. Supabase with local caching ensures the app works with minimal connectivity, mirroring how branch banking systems must operate during network outages. Multi-profile data isolation enforces strict partitioning between users — the mobile equivalent of row-level security.
Architecture Decision
Decision: Supabase with local caching via Capacitor. Rationale: Workout data must be available mid-set regardless of connectivity. Cloud-first with local fallback mirrors how modern banking apps cache critical data — availability over consistency for the user-facing path.
Architecture breakdown
PRIMMO Crafting

AI-powered personal strength coach with tiered routing, event-driven orchestration, and vector search.

Tiered Routing Event-Driven RAG / Vector Search RLS
Next.js TypeScript Supabase OpenAI pgvector
User Query
4-Tier AI
Router
Vector
Search
Event
Orchestrator
RLS-Protected
Storage
Architecture Insight
4-tier AI routing (cache → rules → lightweight model → full model) mirrors how payment systems route transactions through cost-optimized processing tiers. Event-driven orchestration decouples AI inference from data persistence — the same pattern behind CQRS in payment rails. Vector search (RAG) enables semantic retrieval over exercise data, demonstrating enterprise AI patterns. Row-level security enforces per-user data isolation at the database level — identical to how banking systems protect customer data.
Architecture Decision
Decision: 4-tier routing over single-model approach. Rationale: 80% of user queries are repetitive ("log my bench press"). Routing these through cache/rules instead of GPT-4 reduces cost by ~90% — the same cost-optimization logic behind tiered transaction processing in payment gateways.
Architecture breakdown
NoteApp Live

Notes app with multi-tenant row-level security, soft delete, and optimistic auto-save.

Row-Level Security Soft Delete Optimistic Persistence
Next.js TypeScript Supabase TipTap
User Action
Debounced
Auto-Save
RLS Policy
Enforcement
Soft Delete
(Recoverable)
Architecture Insight
Row-level security at the database level ensures users only access their own data — the same Supabase RLS policies used in banking for customer data isolation. Soft delete preserves data for audit and recovery, matching regulatory requirements where financial records must never be permanently destroyed. Debounced auto-save demonstrates optimistic persistence — writes are batched and retried, similar to how transaction systems handle intermittent connectivity.
Architecture Decision
Decision: Soft delete with deleted_at timestamp over hard delete. Rationale: Regulatory audit patterns require data recovery capability. Banking systems never permanently destroy records — they mark them inactive. Same principle applied here for user notes.
Architecture breakdown
Portfolio Optimization Building

Automated portfolio management with strategy pattern, real-time WebSocket streaming, and full cost modeling.

Strategy Pattern (GoF) Real-Time Streaming Domain Modeling
Next.js TypeScript WebSocket Kite API
Market Data
(WebSocket)
Strategy
Engine
Cost Model
(Brokerage+Tax)
Risk
Analytics
Architecture Insight
Strategy pattern (Gang of Four) — pluggable trading algorithms behind a single interface, identical to how banking product engines swap calculation strategies without conditional branching. Real-time WebSocket streaming from Kite Connect demonstrates the same data pipeline patterns used in market data feeds and trading platforms. Full cost modeling (brokerage, STT, GST, stamp duty) mirrors how banking fee engines compute transaction costs across product types.
Architecture Decision
Decision: Strategy pattern over if/else branching for trading algorithms. Rationale: New strategies (iron condor, butterfly) must be pluggable without modifying the engine — identical to how banking product engines add new loan products without changing the core pricing system.
Architecture breakdown
Klarity Building

Task management with 15-stage pipeline, ETag-based distributed sync, and multi-agent orchestration.

Pipeline Pattern Distributed Sync Multi-Agent
Vite React TypeScript Zustand Tauri
Task Input
15-Stage
Pipeline
ETag
Sync
Multi-Agent
Orchestration
Architecture Insight
15-stage pipeline with configurable gates mirrors loan origination workflows and straight-through processing (STP) pipelines in banking. ETag-based sync implements optimistic concurrency control — the same distributed reconciliation pattern used when multiple systems update shared financial records. Multi-agent orchestration via Zustand demonstrates how banking systems coordinate between microservices without tight coupling.
Architecture Decision
Decision: ETag-based optimistic concurrency over pessimistic locking. Rationale: Distributed task sync across devices requires conflict detection without blocking. ETags detect stale writes — the same concurrency model banks use for multi-user account operations where locking would degrade throughput.
Architecture breakdown
Orbit Live

Zero-server mobile companion using GitHub as backend with SHA-based conflict resolution and cross-platform sync.

Zero-Server Architecture Conflict Resolution
React Native Tauri GitHub API
Phone
Client
GitHub
Backend
SHA-Based
Conflict Resolver
Desktop
(Klarity)
Architecture Insight
Zero-server architecture using GitHub as a distributed datastore mirrors how banking settlement systems use existing infrastructure (SWIFT, MEPS+) rather than standing up dedicated servers. SHA-based conflict resolution implements the same content-addressable approach used in Git itself — identical to how banks detect duplicate transactions in multi-channel environments where mobile and branch can modify the same account simultaneously.
Architecture Decision
Decision: GitHub as backend over dedicated server infrastructure. Rationale: Zero infrastructure cost and built-in versioning. SHA-based conflict detection ensures data integrity across devices — the same hash-based reconciliation banks use for cross-channel transaction deduplication.
Architecture breakdown
AnyCalc Live

19 interlinked financial calculators with Plan mode — chain EMI, splits, and conversions. A rule engine in miniature.

Rule Engine Stateless Computation
Next.js TypeScript Supabase Zustand
Input
Expression
Formula
Parser
Stateless
Compute
Deterministic
Output
Architecture Insight
Rule engine pattern — stateless, deterministic computation pipelines identical to how banking product pricing engines compute interest rates, fees, and EMIs. Same input always produces the same output, with no side effects. This is the foundation of every financial calculation engine in banking, from loan EMI calculators to forex rate converters.
Architecture Decision
Decision: Pure functions with zero shared state. Rationale: Financial calculations must be deterministic and auditable. Every EMI, tip split, and conversion in AnyCalc is a pure function — same inputs, same outputs, always. This is non-negotiable in banking computation engines.
Architecture breakdown
Digital Resume Live

Single source of truth architecture — one JSON drives portfolio, resume, and Launchpad dashboard.

Golden Source Multi-Format Rendering
HTML/CSS JavaScript Chart.js JSON
projects.json
(Golden Source)
Portfolio
Cards
/
Resume
Flip-Cards
/
Launchpad
Dashboard
Architecture Insight
Golden source pattern — one projects.json file drives three different outputs (portfolio cards, resume flip-cards, Launchpad status). This is the same pattern banks use for regulatory reporting: a single authoritative data source generates Basel III reports, MAS submissions, and internal dashboards without data duplication or drift.
Architecture Decision
Decision: Single JSON golden source over per-page data duplication. Rationale: Three views (portfolio, resume, Launchpad) consuming different slices of the same data. Duplicating would create drift — the exact problem golden source solves in bank regulatory reporting where one truth feeds multiple downstream consumers.
Architecture breakdown
08.

From the Feed

Project launches, deep-dives, and architectural takes I share on LinkedIn.

Article
I built Klarity — a lightweight personal task board for AI-assisted developers
Read on LinkedIn

A lightweight desktop task board purpose-built for developers who use AI coding assistants. Weighing just 8MB, Klarity runs entirely offline with a 15-stage pipeline that tracks every task from idea to deployment. ETag-based distributed sync keeps your board consistent across machines without a server, while multi-agent orchestration lets different AI assistants collaborate on the same project.

Launch
Launching Orbit — the phone companion for Klarity
Read on LinkedIn

Orbit is the mobile companion for Klarity — letting you review, update, and triage tasks from your phone while the desktop app handles the heavy lifting. Built with a zero-server architecture that uses GitHub as the backend, it achieves sub-2-minute cross-platform sync with SHA-based conflict resolution and zero infrastructure cost.

Article
The Data Problem and its 'Fake' Fix — Synthetic Data for Privacy
Read on LinkedIn

Exploring how synthetic data generation solves one of the hardest problems in enterprise testing — getting realistic test data without exposing real customer information. The article dives into techniques for generating statistically faithful datasets that satisfy GDPR and PII constraints, turning a compliance headache into an engineering advantage.

Insight
AI can write code fast — not necessarily right
Read on LinkedIn

AI can generate code at incredible speed, but speed without structure leads to technical debt just as fast. This post shares a phased workflow with specialized agents (@designer, @architect, @qa) and deliberate human gates at each stage — because the real skill isn't writing code faster, it's knowing when to slow down and verify.

Launch
Meet AnyCalc — the calculator you actually want to use
Read on LinkedIn

AnyCalc packs 19 interlinked financial calculators into a single clean interface — from EMI and tip splits to compound interest and currency conversion. Every calculator feeds into others, so a mortgage estimate can flow into a stamp duty calculation without re-entering numbers. Built to be the one calculator app that actually replaces all the others.

Launch
Shipped my first AI-era side project — a note-taking app in 32 hours
Read on LinkedIn

Shipped a fully functional note-taking app in 32 tracked hours — from blank canvas to production deployment. Features rich text editing with templates, auto-save that never loses a keystroke, and a dark/light theme toggle. The post walks through the experience of building a real product end-to-end with an AI coding assistant for the first time.

Article
Why should you 'Claude' today!
Read on LinkedIn

A candid look at why Claude has become my go-to development partner. This article walks through real examples — from rapid prototyping to production debugging — showing how AI pair programming changes the way you think about building software. It's less about the tool and more about the mindset shift that unlocks a completely different development velocity.

Launch
I just dropped an 8-song album on Spotify — and I've never sung a note
Read on LinkedIn

An 8-song album on Spotify, Apple Music, and Amazon — created by someone who has never sung a note. Each track went through 50+ iterations of prompting, refining, and curating to get the sound right. The post explores what happens when you treat music creation as a creative engineering problem and push the boundaries of what's possible with generative AI.

Post
PyExcel — Revolutionizing spreadsheets with Python
Read on LinkedIn

PyExcel brings the power of Python directly into spreadsheets — letting analysts run ML models, automate transformations, and build dashboards without leaving the tool they already know. The post explores how this shifts the boundary between analysts and engineers, giving non-programmers access to capabilities that previously required a dedicated data team.

Article
The Qualities of a Productive Leader
Read on LinkedIn

A comprehensive breakdown of six qualities that distinguish productive leaders from merely busy ones. From setting clear direction to creating psychological safety, the article draws on real experiences leading cross-functional teams and distills them into actionable principles that any team lead or manager can apply immediately.

Article
SMART — A Simple Hack for All
Read on LinkedIn

SMART (Specific, Measurable, Achievable, Relevant, Time-bound) is one of those frameworks everyone has heard of but few actually apply well. This article shows how to use it beyond the textbook — from writing better OKRs to structuring personal goals that you'll actually follow through on, with practical examples from both professional and personal contexts.

Post
The Samurai with the Wooden Sword
Read on LinkedIn

The story of Miyamoto Musashi — the legendary samurai who defeated opponents using a wooden sword. A reflection on why mastery of fundamentals and strategic thinking will always outweigh having the shiniest tools. The best solutions come from deep understanding of the problem, not from reaching for the most advanced framework.

09.

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