> ## Documentation Index
> Fetch the complete documentation index at: https://docs.onnucleus.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Introduction

> Welcome to the Nucleus Core Banking API platform — built for modern microfinance, commercial, and digital banks.

# Welcome to Nucleus

**Nucleus** is an institutional-grade, multi-tenant core banking engine engineered for high-throughput, double-entry financial accounting, maker-checker governance, and seamless digital banking delivery.

Whether you are launching a digital-first Microfinance Bank (MFB), integrating an existing institution with the Central Bank of Nigeria (CBN) payment rails, or building proprietary mobile and internet banking apps, Nucleus provides the primitives you need.

<CardGroup cols={2}>
  <Card title="Quickstart" icon="bolt" href="/quickstart">
    Set up your credentials and execute your first banking API call in under 5 minutes.
  </Card>

  <Card title="Authentication & Keys" icon="key" href="/authentication">
    Understand the 3 authentication layers: Tenant IDs, Session Tokens, and API Keys.
  </Card>

  <Card title="Digital Banking APIs" icon="mobile" href="/guides/digital-banking-apis">
    Power your custom iOS/Android apps with the headless Self-Service Banking API suite.
  </Card>

  <Card title="API Reference" icon="code" href="/api-reference/overview">
    Browse over 600 interactive OpenAPI 3.0 endpoints across 40+ banking domains.
  </Card>
</CardGroup>

***

## Architectural Principles

<AccordionGroup>
  <Accordion title="Multi-Tenant Isolation" icon="server">
    Every institution runs against a dedicated schema or database partition. Tenancy is strictly isolated at the connection pool, query execution, and encryption levels.
  </Accordion>

  <Accordion title="Immutable Double-Entry Ledger" icon="book">
    All fund movements write balanced debits and credits into the General Ledger (`acc_gl_journal_entry`). Balances are verified deterministically without floating-point rounding errors.
  </Accordion>

  <Accordion title="Maker-Checker Governance (Four-Eyes Principle)" icon="user-check">
    Critical banking operations (large cash withdrawals, loan approvals, teller till closures, custom interest overrides) enforce strict segregation of duties. The user who initiates an operation cannot approve it.
  </Accordion>

  <Accordion title="Regulatory Alignment (CBN & NDIC)" icon="landmark">
    Native support for 10-digit NUBAN generation, 11-digit BVN verification, KYC Tier 1–3 requirements, SCUML compliance, and automated regulatory reporting schedules.
  </Accordion>
</AccordionGroup>

***

## Platform Architecture

```
        ┌──────────────────────────────────────────────────────┐
        │          Nucleus Core Banking Engine :8443           │
        │  GL · Accounts · Loans · Tellers · AML · Interop     │
        └───────┬───────────────────────────────┬──────────────┘
                │                               │
                ▼                               ▼
  ┌───────────────────────────┐   ┌───────────────────────────┐
  │  Staff Console (Web) :3000│   │ Custom Mobile/Web Apps    │
  │  Branch Ops · Maker-Check │   │ Customer Digital Banking  │
  └───────────────────────────┘   └───────────────────────────┘
```