The Landscape of Core Banking Developers: Building Financial Systems from Scratch

Tuấn Anh — Sat, 06 Jun 2026 15:17:38 +0000

This post is the Executive Summary of my 8-part long-form series: *Learning Path to Become a Core Banking Developer** originally published on my blog.*

Who is a Core Banking Developer?

A Core Banking Developer is a software engineer responsible for building, operating, and extending the system that processes all of a bank's core financial operations — from managing accounts, processing money transfers, and calculating interest rates, to ensuring every single penny is recorded with absolute accuracy.

Unlike a typical developer, a mistake for a Core Banking Developer doesn't just mean a 404 error page — it means customers' money being lost, duplicated, or the general ledger becoming unbalanced. This intense pressure defines their entire approach to writing code and designing systems.

Why is this field special?

1. Absolute Accuracy

In regular software development, "eventual consistency" is often acceptable. In Core Banking, a transaction either completely succeeds or does not happen at all. There is no in-between state. This is why ACID database transactions are an indispensable foundation.

2. Extremely High Concurrency

Millions of users can perform transactions simultaneously within the same second. The system must handle concurrency without allowing race conditions that could lead to incorrect deductions or double credits.

3. Compliance and Legal Requirements

Every action in a Core Banking system must have an audit trail. The State Bank, tax authorities, and international organizations reserve the right to review the entire transaction history at any given time.

The Knowledge Map of a Core Banking Developer

If you want to transition from a regular backend engineer to a financial systems architect, you need to bridge both domain knowledge and heavy technical architecture.

┌─────────────────────────────────────────────────────────────────┐
│                   CORE BANKING DEVELOPER                        │
│                                                                 │
│  DOMAIN KNOWLEDGE          TECHNICAL SKILLS                     │
│  ─────────────────          ────────────────                    │
│  • Double-Entry (GL)       • Database (ACID, Locking)           │
│  • CASA (Deposits)         • Distributed Transactions           │
│  • Lending (Credit)        • Event-Driven Architecture          │
│  • Payments & Clearing     • API Design (REST/gRPC)             │
│  • Trade Finance           • Security & Encryption              │
│                                                                 │
│  STANDARDS & PROTOCOLS     ARCHITECTURE PATTERNS                │
│  ─────────────────────     ─────────────────────                │
│  • ISO 8583 (Card/ATM)     • Saga Pattern                       │
│  • ISO 20022 (SWIFT)       • Outbox Pattern                     │
│  • BIAN Framework          • CQRS & Event Sourcing              │
│  • PCI-DSS                 • Idempotency Keys                   │
└─────────────────────────────────────────────────────────────────┘

The Market Landscape

Popular Core Banking Systems

To understand the ecosystem, here are the dominant legacy and modern systems you will encounter in the banking industry (with examples of adoptions in regional markets like Vietnam):

System	Core Technology	Banks Using It
Temenos T24	Java, jBASE/BASIC	Techcombank, VPBank, MB Bank, Sacombank
Oracle Flexcube	Java EE, Oracle DB	VietinBank, BIDV
Infosys Finacle	Java	Agribank (Under deployment)
In-house (Custom)	Go, Java, Kotlin	MoMo, ZaloPay, VCB Digibank

Next-Generation Trends

Digital banks and fintechs are no longer purchasing off-the-shelf monolithic Core Banking systems — they are building their own Core Banking systems using Microservices. This represents a massive opportunity for full-stack developers with a mindset for distributed systems.

Ready to dive deeper?

This was just the executive summary. If you want to actually build these systems, I have written a complete step-by-step roadmap for developers:

Part 1 — The Double-Entry Ledger Foundation (The mental foundation you cannot skip)
Part 2 — Core Banking Domain: CASA & Lending
Part 3 — Database Design for Financial Transactions
Part 4 — Modern Core Banking Architecture
Part 5 — International Integration Standards (ISO 8583)
Part 6 — Security, Compliance & Audit
Part 7 — Build a Mini Core Banking System from Scratch

👉 Read the full 8-part series on my blog

I'm Lê Tuấn Anh, a Go Backend Architect specializing in microservices migrations and financial platforms. If you found this useful, let's connect on LinkedIn.

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