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We modernized a legacy Python SDK into a modular JavaScript solution with real-time streaming capabilities. This expanded access to the financial data API and positioned the platform for scalable API monetization.
The client is a financial media company based in the United States, offering financial media services, stock market analytics, and financial news. They provide real-time stock market updates, stock activity monitoring, as well as historical stock market data for financial sites and trading applications.
The company planned to extend its internal data capabilities into an external financial data API offering to reach developers, fintech startups, and analytics platforms. Their core challenge was a legacy Python-centric integration layer that limited their reach.
The client had an existing mature internal data infrastructure, although its external distribution potential was limited.
The original SDK was built primarily for Python-based environments. However, the mass market for trading platforms and financial dashboards is heavily oriented toward JavaScript frameworks and Node.js-based backends.
This misalignment created integration friction. Developers working in web-based environments faced additional adaptation effort when integrating the financial data API into their applications. Improving developer experience became directly linked to unlocking API monetization and growth.
The Client couldn’t use off-the-shelf wrappers because of the platform-specific market data aggregation logic, real-time feeds, and domain-specific endpoints. The SDK must provide structured access, along with a degree of flexibility, for different integration scenarios.
Without a modular and ecosystem-aligned solution, external adoption would remain limited.
The goal was to combine scattered Python wrappers into a unified JavaScript/TypeScript SDK:
The unified JavaScript/TypeScript SDK would act as the primary interface for interacting with the client’s financial data services.
The solution required structured WebSocket-based real-time streaming to support continuous market updates.
Stability and predictability were key requirements for data delivery for external developers who would be working with this financial data API.
Market data endpoints, access to historical data, and news services were consolidated as part of this project.
A team of specialists took on the challenge of turning large financial datasets into a simple, high-performance product that developers actually enjoy using.
Project ManagerCoordinated delivery in Agile sprints and aligned SDK modernization milestones with the client’s product roadmap.
Business AnalystDefined SDK requirements, analyzed integration pain points, and structured API monetization capabilities for broader market adoption.
Solution ArchitectDesigned the modular architecture of the JavaScript SDK and defined the real-time streaming integration strategy.
Backend EngineersDeveloped the SDK core logic, implemented WebSocket-based real-time streaming, and structured market data aggregation modules.
DevOps EngineerSet up CI/CD pipelines using GitLab and managed npm package distribution for controlled releases.
QA Manual and Automation EngineerValidated SDK functionality, integration stability, and data consistency across real-time and historical endpoints.
The solution brings together backend market data processing with a JavaScript SDK that is designed to be scalable for API distribution to other developers.
Backend services, partially implemented in Go, handle market data aggregation and processing of real-time and historical financial data.
Instead of distributing a monolithic package, the system is structured into independent modules covering real-time data, historical endpoints, and additional API services. This approach:
Simplifies integration
Improves maintainability
Enables independent feature expansion
Supports controlled versioning
The modular design ensures that new data capabilities can be introduced without disrupting existing integrations, providing a scalable foundation for long-term API growth.
Our development and integration experts implemented real-time streaming using WebSockets to support the continuous delivery of live market data.
This approach eliminates the need for repeated polling requests and provides developers with a structured method for receiving live stock updates within their applications.
The streaming layer is fully integrated into the SDK, allowing external teams to work with real-time and historical endpoints through a unified interface. This consistency improves the overall developer experience and supports high-frequency data use cases.
The backend layer is responsible for handling API requests and processing high-frequency market data in a stable manner for both real-time and historical APIs.
Secure authentication processes are in place for the financial data API, and GitLab CI/CD pipelines are used for structured release and version management of the SDK packaged with npm.
This architecture brings together backend processing, streaming, and SDK distribution to create a unified system for scalable API integration solutions.
The project followed a predictable lifecycle of discovery through final QA validation to ensure that the output of the project was technically sound and met all of the business KPIs.
The team analyzed the legacy Python SDK to identify architectural constraints and integration limitations. The objective was to define requirements for a JavaScript-based SDK to improve the developer experience and expand access to the financial data API.
TypeScript was selected to provide typed interfaces and structured SDK usage. The Solution Architect designed a modular architecture that allows developers to import only the required components.
The backend development experts were responsible for creating the authentication mechanisms and incorporating WebSocket-based real-time streaming.
The SDK was structured into independent modules covering real-time market data, historical endpoints, and additional API services. This approach improved flexibility and maintainability.
Manual and automated testing ensured stable API interaction across real-time and historical data endpoints before release.
Jelvix’s specialists developed technical documentation for the SDK and released it via npm. The release process was done via GitLab CI/CD pipelines.
The modernization of the SDK removed architectural constraints that had previously restricted the distribution of APIs. By improving the developer experience and offering a modular architecture with real-time streaming support, the client made its financial API more accessible throughout the JavaScript developer community.
The solution delivered the full scope of defined functional requirements and established a scalable foundation for API monetization and broader market adoption.
The new JavaScript SDK removed integration barriers and made it easier for external teams to adopt and build on the platform’s market data services.
Unlocked a Global Audience of 25M+Transformed the financial data API from a niche tool to a global resource, delivering trusted financial information to readers in 125 countries.
Open Access for DevelopersThe modular JavaScript SDK broke the Python-only barrier, opening the API to the world’s largest developer community and enabling mass-market adoption.
Monetization-Ready CoreEngineered a high-variability SDK that directly improves API monetization and adoption and strengthens the commercial offer for institutional and retail partners.
Zero-Friction IntegrationBuilt a low-code-friendly architecture that allows external teams to add real-time market insights to their projects without deep engineering overhead.
Consulting first with an industry leader before charging ahead means you’ll know your customers truly want your product instead of hoping they will.
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