The Modern Full Stack Approach to Banking | Cross River Operating System (COS) 

Cross River

October 16, 2023

6 min read

Hello, COS 

The emergence of innovative fintech companies brought an unprecedented verticalization of banking services. While traditional banks solve for distribution, new fintechs solve for user pain points, shifting the requirements for the sponsor bank from standardized banking services to customized and event-driven solutions.  

These specialized offerings changed the banking landscape into thinking in different layers: the basic infrastructure layer, the banking-as-a-service technology layer, and the customer-facing application layer.


The result of the common ‘Fintech-Tech Middleware-Sponsor Bank’ partnership created a fragmented solution, requiring fintechs to work with multiple partners to offer an integrative financial experience to their users. And when the sponsor bank is intermediated by a middleware technology provider, things break, and end users feel the pain. 

To solve this challenge, in 2018 Cross River supplemented its already strong set of banking operations with a proprietary, modular, and event-driven core banking system called COS. Exposed through RESTful APIs, COS brings to the market a solid, reliable, and adaptable solution to enable fintech companies the ability to offer legacy and new banking services in the most efficient, safe, flexible, and customized way. The combination of the regulatory framework and the technology layer makes Cross River a tech-forward, licensed one-stop-shop. 

 COS was built internally from the ground-up to meet the needs of innovative and forward-thinking technology companies. The most distinctive feature of COS is Cross River’s total ownership of the system; it is independent of any external system and therefore doesn’t hold any legacy challenges. This ownership allows the system to be integrable, modular, customizable, scalable, engineer-friendly, and future-proof.


System Highlights 

Cross River combines the best of both worlds – technology support coupled with banking expertise. 

  • COS enables Cross River to provide premium, high-tech solutions for online banking and payment operating systems. 

  • COS special purpose accounts can easily be customized to function within defined parameters and varied interest rates. Business customers can define and redefine financial products to adapt to evolving markets with the robust set of COS API calls. 

  • COS is built with regulatory compliance and consumer protection top of mind. Direct connectivity to the core also ensures secure, efficient transactions as every API call is digitally signed to ensure non-repudiation and optimum security. 

  • COS is developed and designed with elegant connectivity to a wide array of banking rails including ACH, wires, and the major card networks. Business customers benefit from the simplicity of one platform for all banking transactions combined with premium speed, advantageous cost, and intuitive interfaces. 

  • COS encourages business customers to create unique interfaces, dashboards, and analytic tools as the API sets are designed with big data in mind. 

  • Business customers can offer FDIC-insured accounts that function as mobile wallets with COS mobile application integration. COS substantially reduces the current cost of virtual mobile wallet transaction fees by cutting out the middlemen. 

  • COS minimizes the large volume of paperwork associated with other wire systems and creates an intelligent digital process for all wire transactions. 

 Other Highlights of COS: 

  • Ability to instantly scale up virtual accounts  

  • Enriches the relationship between partners and Cross River  

  • Broad customer base [3.3 million customers onboarded since launch] 

  • 24/7 monitoring and support 

  • Ease of integration and implementation


Tech Features1 

COS offers robust ready-to-use API-based capabilities and advantages to developers, including: 

  • Webhook: Webhook events to update customers and developers regarding important events and changes within the core via real-time notifications, eliminating the need to poll the API to track changes and updates. 

  • Sub-Ledgers  COS offers the ability to createsub-ledgers instantly and on-demand. A sub-ledger can be linked to any existing deposit account, also known as the master account. Each master account has what is called an "implicit" sub-ledger, which is automatically created and maintained. 

  • COS Explorer: Facility for partners to review transactions, create customer accounts and initiate payments via a permission-based UI.  

  • Integration with Compliance Tools: Customizable, secured, and compliance-ready banking services which minimize loss from fraud and cyber-security threats 

  • Customized Accounts: Special purpose accounts that can be customized to work within defined parameters and interest rates 

  • Web-based Operations Portal: Facility for businesses to manage their fintech programs and originate transactions


Example Use Cases 

Banking as a Service (BaaS)  A BaaS platform allows a partner to offer their customers or businesses traditional banking products. The BaaS platform onboards customers and businesses as customers in COS, and for each customer a master account under that product is opened. Examples of BaaS use cases:  

  • Online lending companies and small businesses offering bank accounts to their borrowers  

  • Digital financial services companies using their own front-end/UI, integrated with Cross River’s back-end banking infrastructure, to offer business banking and business co-branded cards 

  • Wealth management and personal financial management applications offering bank accounts and debit cards to customers  


 A 3rd-party service provider (TPSP)  A 3rd-party service provider can offer its technology services to another company, which can then use the technology to provide services to its consumers.  

For example, a COS BaaS partner may want to offer their customers the ability to pay bills in their app. In this scenario, the third-party service provider has a direct connection to the RPPS  

 The BaaS partner can onboard each customer and open an account in COS. When the consumer pays a bill, the bill pay app is directly integrated with the 3rd-party provider and the customer will be able to use the app to pay their bills. 


Principles COS is built with six principles in mind: 

  • Integrability  

COS can be integrated with a variety of third-party software platforms. This makes it an attractive option for fintech startups and businesses to offer banking services to their customers. In the case of Cross River, existing partners include Coinbase, Stripe, and Affirm. 

  • Bespoke Solutions/Lego Bricks for Your Fintech Innovation 

Businesses can work with Cross River to create bespoke solutions that meet their unique needs. This is particularly useful for businesses that require specific functionality or workflows that are not available in off-the-shelf banking offerings.  

  • Module-based Customization  

COS is built on a microservices architecture and includes a range of modules that support various banking functions. Some of these modules include account management, transaction processing, and compliance monitoring. The modular nature of COS allows businesses to select only the desired modules without having to pay for unneeded features.  

  • Fast and Scalable Processing  

COS serves high-speed payment originations. Transactions are cleared and settled across peer-to-peer customer ledgers and high-speed transaction messaging. By speeding up the process of money movement, COS can process large volumes of transactions and provide real-time data to its clients. This can also be applied to clients’ businesses, where COS can accommodate high-volume transactions. 

  • Developer Friendly 

The APIs provide comprehensive documentation, sample code, and a sandbox environment for testing, making it easy for developers to start building quickly. 

  • Future-proof 

Cross River regularly adds and updates modules to ensure the system meets the changing needs of clients. Our partners can be confident that the banking solutions they create using the COS will continue to be effective and efficient into the future.


As fintech continues to evolve, digital tools like APIs will play an important role in aiding businesses to offer cutting-edge financial solutions to their customers. Cross River’s COS is an integrable, customizable, and secure API-driven banking core that brings an all-inclusive banking experience to fintechs and businesses. 

Learn more about COS.



1 COS enables the creation of products, such as virtual wallets, sub-accounts, and special-purpose accounts. The final configuration of products and services will depend on the partner's agreement with CRB.