FinTech / Business Ledger

Outstanding Manager (FinTech Utility)

A specialized financial management tool for local businesses to track credits, debits, and outstanding balances. It features a rapid AI-driven entry system and a precise FIFO (First-In-First-Out) payment allocation engine.

FlutterRiverpodFirebaseCloud Functions

View Repository

Technical Specifications

Language

Dart

Architecture

Repository Pattern / Clean UI

Key Interface

Riverpod State Management

Platform

Android / iOS

Key Engineering Achievements

AI-powered rapid entry agent
Precise FIFO payment allocation
Real-time ledger with automated balances
Multi-party transaction history

Technical Deep Dives

A granular analysis of the engineering hurdles encountered during development and the architectural decisions made to resolve them at scale.

Challenge 01

ACID-Compliant Ledger

The Problem

Guaranteed atomicity in financial entries to prevent balance mismatches during local-to-cloud synchronization especially in flaky network conditions.

Engineering Decision

Utilized Firestore WriteBatch to ensure every ledger entry and its corresponding aggregate balance update succeed or fail together.

Implementation

The repository layer wraps the transaction creation and running balance update in a single atomic WriteBatch.

Tech Stack snippet

final batch = firestore.batch();
batch.set(entryRef, entry.toMap());
batch.update(accountRef, {
  'outstandingBalance': FieldValue.increment(entry.amount),
});
await batch.commit();

Challenge 02

FIFO Payment Allocation

The Problem

Developed a First-In, First-Out algorithm to automatically distribute partial payments across multiple unpaid invoices based on age.

Engineering Decision

Designed an in-memory greedy allocation algorithm that pre-calculates the debt distribution before document creation.

Implementation

The allocation engine iterates through a chronologically sorted invoice list to distribute the incoming payment amount precisely.

Tech Stack snippet

for (var invoice in invoices) {
  if (remainingAmount <= 0) break;
  double allocateToThis = min(remainingAmount, invoice.outstandingAmount);
  allocations.add(PaymentAllocation(
    invoiceId: invoice.id,
    allocatedAmount: allocateToThis,
  ));
  remainingAmount -= allocateToThis;
}

Challenge 03

Dataset Virtualization

The Problem

Optimized the rendering of transaction histories with 1000+ entries using list virtualization for 60fps performance on budget devices.

Engineering Decision

Implemented Sliver-based lazy loading in Flutter to ensure only visible items are kept in memory.

Implementation

The ledger screen performs a linear aggregation and uses CustomScrollView with slivers to avoid O(N²) calculation overhead during scroll events.

Tech Stack snippet

CustomScrollView(
  slivers: [
    SliverList(
      delegate: SliverChildBuilderDelegate(
        (context, index) => LedgerRow(entries[index]),
        childCount: entries.length,
      ),
    ),
  ],
)