How to Build a Neobank Technology Stack (Core, Ledger, Cards, Compliance)

Building a Neobank Technology Stack: Key Components and Requirements

Neobanks require a multi-layered technology architecture that handles customer-facing operations, regulatory compliance, and core banking functions. Unlike traditional banks that rely on monolithic legacy systems, neobanks build modular stacks that integrate specialized fintech services through APIs.

The core challenge lies in selecting components that balance feature richness with integration complexity. Each layer—from user interface to core ledger—must communicate seamlessly while meeting stringent security and compliance requirements.

Step 1: Select Your Core Banking Platform

The core banking system handles account management, transaction processing, and customer data storage. Neobanks typically choose between building in-house or using Banking-as-a-Service (BaaS) providers.

BaaS Provider Options:

• Synapse: Offers deposit accounts, ACH processing, and card issuing through partner banks.
• Unit: Provides checking accounts, savings, and business banking features. Their sandbox environment includes test routing numbers and mock transaction data for development.
• Cross River Bank: Direct bank partnership offering FDIC-insured accounts and real-time payment processing.

In-House Development Considerations:

Building your own core requires a banking license. However, this approach offers complete control over features and customer experience.

Step 2: Implement General Ledger and Accounting Systems

The general ledger tracks all financial transactions and maintains regulatory reporting capabilities. Modern neobanks use double-entry bookkeeping systems with real-time transaction posting.

Technical Requirements:

• Support multiple currencies and exchange rate calculations
• Generate ACH, wire transfer, and card transaction records
• Maintain audit trails for all account modifications

Popular Ledger Solutions:

• Mambu: Cloud-native system supporting deposits, loans, and investment products. API-first architecture with pre-built connectors for payment processors and compliance tools.
• Thought Machine Vault: Real-time processing engine handling very high transaction throughput. Smart contracts feature allows custom business logic implementation.
• Custom Development: PostgreSQL or MongoDB databases with event-sourcing patterns.

Step 3: Integrate Card Issuing and Payment Processing

Card programs require partnerships with licensed issuers and payment processors. The integration involves three main components: card issuance, transaction authorization, and settlement processing.

Card Issuing Partners:

Implementation Process:

1. Submit program application with business model details and expected transaction volumes
2. Complete compliance review including KYC procedures and fraud monitoring systems
3. Integrate card management APIs for account linking, spending controls, and transaction webhooks
4. Configure card designs and delivery methods (physical and virtual cards)
5. Test authorization flows using provided sandbox environments

Payment Processing Setup:

ACH processing requires a Third Party Service Provider (TPSP) registration with NACHA. Direct FedACH participation carries modest per-item fees (a fraction of a cent each, volume-tiered) plus monthly participation fees, while building and integrating the connection typically requires additional one-time and ongoing investment.

Wire transfers need SWIFT network access through correspondent banking relationships.

Step 4: Build Compliance and Risk Management Framework

Regulatory compliance encompasses KYC/AML procedures, transaction monitoring, and reporting requirements. Neobanks must implement these systems before processing their first customer transaction.

KYC/AML Implementation:

• Identity Verification: Integrate services like Jumio, Onfido, or Persona for document scanning and biometric verification. These platforms verify government IDs rapidly and with high accuracy.
• Customer Risk Scoring: Use LexisNexis Risk Solutions or Thomson Reuters World-Check for sanctions screening and PEP identification.
• Transaction Monitoring: Implement rule-based systems detecting structuring, unusual velocity, or geographic anomalies. Popular solutions include NICE Actimize, SAS Anti-Money Laundering, and Featurespace ARIC.

Reporting Requirements:

Currency Transaction Reports (CTRs) must be filed for cash transactions exceeding $10,000. Suspicious Activity Reports (SARs) require filing within 30 days of detection. Both reports submit through FinCEN's BSA E-Filing System using XML format specifications.

Data Protection Compliance:

Implement PCI DSS Level 1 compliance for card data handling. This requires quarterly vulnerability scans, annual penetration testing, and network segmentation between card processing and other systems.

Step 5: Develop Customer-Facing Applications

The mobile and web applications serve as the primary customer interface. Modern neobanks prioritize mobile-first design with progressive web app capabilities for desktop access.

Technical Architecture:

• Frontend Framework: React Native or Flutter for cross-platform mobile apps. Native iOS (Swift) and Android (Kotlin) development for performance-critical features.
• API Gateway: Kong, AWS API Gateway, or Apigee for request routing, authentication, and rate limiting. Configure 1,000 requests per minute limits for individual users.
• Authentication: OAuth 2.0 with PKCE for mobile apps. Multi-factor authentication using SMS, email, or authenticator apps. Biometric authentication (TouchID/FaceID) for transaction approval.

Core Features Implementation:

• Account Dashboard: Real-time balance updates via WebSocket connections. Transaction categorization using Plaid, Yodlee, or custom machine learning models.
• P2P Payments: Zelle integration through Early Warning Services or custom solutions using phone number/email lookup systems.
• Bill Pay: Integration with CheckFree, Fiserv, or Paymi for payee database and payment processing. Support for one-time and recurring payments.
• Budget Tools: Spending analysis based on merchant category codes (MCCs). Goal-setting features with automated savings transfers.

Step 6: Establish Operational Infrastructure

Neobanks require 24/7 operational monitoring, customer support systems, and disaster recovery procedures. This infrastructure supports both customer-facing services and regulatory requirements.

Monitoring and Alerting:

• Deploy application performance monitoring using Datadog, New Relic, or Splunk
• Set up transaction failure alerts with escalation procedures for payment processing issues
• Configure database replication across multiple availability zones
• Implement automated scaling for traffic spikes during promotional campaigns

Customer Support Integration:

• Zendesk or Salesforce Service Cloud for ticket management
• Screen sharing capabilities for mobile app troubleshooting
• Integration with core banking APIs for account research and transaction disputes

Business Continuity Planning:

Recovery objectives for critical systems require primary and secondary data centers with real-time replication.

Technology Stack Integration and Testing

The final implementation phase involves end-to-end testing and gradual rollout.

Integration Testing Checklist:

Performance Benchmarks:

For organizations seeking guidance on core banking system selection and implementation, detailed feature checklists for core banking software can streamline the evaluation process. Additionally, transformation toolkits provide structured methodologies for migrating from legacy systems or launching new digital banking platforms.