Architecture
Detailed architecture documentation — HLD, LLD, ADRs, Integration, Database
Overview
Architecture documentation index
High-Level Design (HLD)
System-level architecture diagrams and design
System Context
System Context Diagram (C4 Level 1) Document: HLD-001 Status: Approved Last updated: 2026-02-21 A...
Container Diagram
C4 Level 2 — Container Diagram Drop fintech platform container architecture showing all runtime ...
Component Overview
Component Overview (C4 Level 3) Document: HLD-002 Version: 1.0 Date: 2026-02-21 Author: Frontend ...
Deployment Architecture
Deployment Architecture AWS deployment topology, Cloudflare edge layer, Docker multi-stage build...
Security Architecture
Security Architecture — High-Level Design Version: 1.0 Date: 2026-02-21 Author: Banking Architect...
Data Architecture
Data Architecture Version: 1.0 Date: 2026-02-21 Status: Approved Owner: Database Architect Overv...
Low-Level Design (LLD)
Detailed flow diagrams and implementation details
Login & Authentication Flow
Flow: Login & Authentication Document: LLD-001 Version: 1.0 Date: 2026-02-21 Author: Frontend Arc...
Login & Authentication (Backend)
Login & Authentication — Backend Architecture Backend-specific authentication details for the Dr...
Registration & Onboarding Flow
Registration & Onboarding Flow -- Low-Level Design Document: LLD-REGISTRATION Status: Approved La...
KYC & AML Flow
KYC/AML Flow -- Low-Level Design Document: LLD-KYC-AML Status: Approved Last updated: 2026-02-21 ...
Bank Account Linking Flow
Low-Level Design: Bank Account Linking Flow Version: 1.0 Date: 2026-02-21 Author: Banking Archite...
QR Payment Flow
Flow: QR Payment Document: LLD-002 Version: 1.0 Date: 2026-02-21 Author: Frontend Architect (AI A...
Remittance Flow
Low-Level Design: Remittance Flow Version: 1.0 Date: 2026-02-21 Author: Banking Architecture Team...
Merchant Onboarding Flow
Flow: Merchant Onboarding Document: LLD-006 Version: 1.0 Date: 2026-02-21 Author: Frontend Archit...
Transaction History Flow
Flow: Transaction History Document: LLD-003 Version: 1.0 Date: 2026-02-21 Author: Frontend Archit...
Profile & Settings Flow
Flow: Profile & Settings Document: LLD-004 Version: 1.0 Date: 2026-02-21 Author: Frontend Archite...
Notifications Flow
Flow: Notifications Document: LLD-005 Version: 1.0 Date: 2026-02-21 Author: Frontend Architect (A...
Low-Level Design Document
Low-Level Design Document Project: Drop Module/Component: Transactions Module (Remittance + QR P...
LLD: Withdrawal Flow
Withdrawal Request Flow (Angrerett) Purpose Implements the user's right of withdrawal (angrerett)...
LLD: Middleware Lifecycle Flow
Middleware Lifecycle — Low-Level Design Document: LLD-MIDDLEWARE Status: Approved Last updated: 2...
Architecture Decision Records (ADR)
All architectural decisions and rationale
Architecture Decision Record — ADR-013
Architecture Decision Record — ADR-013 Project: Drop ADR Number: ADR-013 Title: Neonomics as Ope...
ADR-001: Consolidate Backends
ADR-001: Consolidate to Single Backend Status: Accepted Date: 2026-02-12 Deciders: John (AI Direc...
ADR-002: Separate FonTelePay
ADR-002: Separate FontelePay from Drop Repository Status: Accepted Date: 2026-02-12 Deciders: Joh...
ADR-003: PSD2 Pass-Through Model
ADR-003: Adopt PSD2 Pass-through Model (No Wallet) Status: Accepted Date: 2026-02-12 Deciders: Al...
ADR-004: JWT HTTPOnly Cookies
ADR-004: JWT Storage in httpOnly Cookies Status: Accepted Date: 2026-02-21 Deciders: John (AI Dir...
ADR-005: Monolith First
ADR-005: Monolith-First Architecture Status: Accepted Date: 2026-02-21 Deciders: John (AI Directo...
ADR-006: SQLite to PostgreSQL
ADR-006: SQLite for Development, PostgreSQL for Production Status: SUPERSEDED by ADR-014: Postgre...
ADR-007: BankID OIDC Auth
ADR-007: BankID as Sole Authentication Provider Status: Accepted Date: 2026-02-21 Deciders: Alem ...
ADR-008: Hono API Framework
ADR-008: Hono v4 for Mobile API Status: Accepted Date: 2026-02-21 Deciders: John (AI Director) Ca...
ADR-009: Feature Flag System
ADR-009: Custom Feature Flag System Status: Accepted Date: 2026-02-21 Deciders: John (AI Director...
ADR-010: Dual Database Driver
ADR-010: Dual Database Driver Abstraction Status: SUPERSEDED by ADR-014: PostgreSQL-Only Architec...
ADR-011: Expo Mobile Framework
ADR-011: Expo SDK 54 for Mobile App Status: Accepted Date: 2026-02-21 Deciders: John (AI Director...
ADR-012: AWS App Runner Deploy
ADR-012: AWS App Runner for Deployment Status: Accepted Date: 2026-02-21 Deciders: John (AI Direc...
ADR Overview
Architecture Decision Records (ADRs) Project: Drop -- Fintech Payment App Last updated: 2026-03-0...
Integration Specifications
Third-party integration architecture and flows
BankID OIDC Integration
BankID OIDC Integration Version: 1.0 Date: 2026-02-21 Author: Banking Architecture Team Status: A...
Open Banking (AISP/PISP)
Open Banking Integration: AISP & PISP Version: 1.0 Date: 2026-02-21 Author: Banking Architecture ...
Payment Processing
Payment Processing Architecture Version: 1.0 Date: 2026-02-21 Author: Banking Architecture Team S...
Sentry Observability
Sentry Observability Integration Error tracking, performance monitoring, alerting, and SLO/SLI d...
Sumsub KYC Integration
Sumsub KYC/AML Integration Identity verification architecture for the Drop fintech platform usin...
AISP Registration Serbia — NBS Response (Tok)
AISP Registracija u Srbiji — NBS Odgovor Datum: 2026-03-18 Izvor: Narodna Banka Srbije (platni.si...
Database Architecture
Database design, migration strategy, lifecycle, audit, indexing
Database Design
Database Design Version: 1.0 Date: 2026-02-21 Status: Approved Owner: Database Architect Design ...
Migration Strategy
Migration Strategy: SQLite to PostgreSQL STATUS: COMPLETED (2026-03-03) This document describes ...
Data Lifecycle
Data Lifecycle Management Version: 1.0 Date: 2026-02-21 Status: Approved Owner: Database Architec...
Audit Architecture
Audit Architecture Version: 1.0 Date: 2026-02-21 Status: Approved Owner: Database Architect Over...
Indexing Strategy
Indexing Strategy Version: 1.0 Date: 2026-02-21 Status: Approved Owner: Database Architect Overv...
High-Level Design Document
High-Level Design Document Project: Drop Version: 1.0 Date: 2026-02-23 Author: Petter Graff, Sen...
Low-Level Design (LLD)
Low-Level Design Document Project: {{PROJECT_NAME}} Module/Component: {{MODULE_NAME}} Version: {...
Architecture Decision Record (ADR)
Architecture Decision Record — ADR-{{NUMBER}} Project: {{PROJECT_NAME}} ADR Number: ADR-{{NUMBER...
Module Design Document
Module Design Document Project: Drop Module: Payments Module (transactions + recipients + exchan...
Integration Design Document
Integration Design Document Project: Drop Integration: BankID OIDC + Open Banking (Neonomics AIS...
Data Flow Document
Data Flow Document Project: {{PROJECT_NAME}} Version: {{VERSION}} Date: {{DATE}} Author: {{AUTHO...
API Specification
API Specification Project: {{PROJECT_NAME}} API Name: {{API_NAME}} Version: {{API_VERSION}} Date...
Database Schema Document
Database Schema Document Project: {{PROJECT_NAME}} Database: {{DATABASE_NAME}} Version: {{VERSIO...
High-Level Design (HLD)
High-Level Design Document Project: {{PROJECT_NAME}} Version: {{VERSION}} Date: {{DATE}} Author:...
Module Design
Module Design Document Project: {{PROJECT_NAME}} Module: {{MODULE_NAME}} Service: {{SERVICE_NAME...
Integration Design
Integration Design Document Project: {{PROJECT_NAME}} Integration: {{INTEGRATION_NAME}} Version:...