# Juan Adan — Senior Software Engineer (Full Stack) > Nine years designing and evolving business-critical systems across financial, > lending and healthcare platforms. Specialized in .NET and Angular, hands-on > with ReactJS and NodeJS, with a strong focus on backend and RESTful API > design. Based in Cuernavaca, Mexico, working with US-based teams in full > time-zone alignment. This file is the plain-text version of https://adanjuanj.com, provided for crawlers, language models and anyone who prefers text. It is the authoritative version: the HTML page presents the same work history as a stylised `git log`, which is a visual device only. ## How to read the work history Both of Juan's employers are **software consultancies**, so every role has two company names: - **Employer** — who paid him: Tech9, or CrossBridge Technology Solutions. - **Client** — the company whose product he worked on during that engagement. On the website these appear as git decorations: the employer is the commit title, the client is a `client/...` branch ref, and the `tag: vYYYY.MM` is the role's start date. The seven-character hex strings are decorative and carry no meaning. Engagements at CrossBridge **overlap during 2018–2019**. This is not an error: they were concurrent client projects under a single employer. Where one role's end month equals the next role's start month — May 2022, and December 2025 — that month is the transition between the two roles, not an overlap or a gap. ## Contact - Name: Juan Adan - Email: adanjuanj@gmail.com - Location: Cuernavaca, Morelos, Mexico - Website: https://adanjuanj.com - Current title: Senior Software Engineer - Current employer: Tech9 - Open to: backend and platform engineering, framework modernization, technical leadership ## Summary Full Stack Software Engineer with nine years of professional experience (since January 2017). Builds and modernizes the systems companies run on: vehicle lending pipelines, underwriting and decisioning engines, patient financing platforms and healthcare applications. Strongest in backend work — .NET, RESTful API design, microservices and rules engines — with production Angular and React on the front end. Repeated track record of taking legacy systems across major framework generations without functional regression, and of building greenfield services that moved measurable business numbers. ## Work history ### Tech9 — Senior Software Engineer - Employer: Tech9 (consultancy) - Client: VCA Animal Hospitals - Dates: 2025-12 to present - Stack: .NET 10, Angular 22, PostgreSQL, Azure, GitHub Copilot, Claude Platform modernization on the Scribe application. - Introduced Clean Architecture patterns to the Scribe platform modernization, establishing a standardized codebase structure now adopted across multiple VCA projects. - Designed and executed the migration of a healthcare care-planning application from Angular 6 to Angular 22, and from .NET Framework 4.6.2 to .NET 10 — four major framework generations — resolving framework-level breaking changes and dependency conflicts while maintaining complete functional parity with the legacy system. ### Tech9 — Senior Software Engineer - Employer: Tech9 (consultancy) - Client: Prestige Financial Services (vehicle lending) - Dates: 2022-05 to 2025-12 (3 years 7 months) - Stack: .NET 8, NestJS, Angular 15, Blazor, ReactJS, SignalR, SQL Server, MongoDB, CosmosDB, RabbitMQ, AWS, Azure, Pulumi, GitHub Copilot Owned large parts of the vehicle lending pipeline end to end. - Built **LeadSpy**, a NestJS lead-acquisition platform that streamlined the application process for used and new vehicle loans, contributing to **60,000 new deals financed in the first two quarters of 2025**. Integrated it into the Partner API Gateway with adverse-action publishing via RabbitMQ, VIN validation and lead decline logic. - Co-developed the **Customer Web App and Interview API** from scratch, enabling digital submission with progress tracking, roadblock automation and communication preferences — producing a **60% increase in funded deals in the first week of launch**. - Built the **Lending Program rules engine** from scratch: credit tier rules, MaxTerm/MaxAPR calculations, dealer tier validations, LTV rules and state-level overrides, replacing a legacy static matrix with a configurable, migration-driven system. - Maintained and evolved **DealIQ and the Structure API** — core systems calculating contract financial terms, fee adjustments, GAP validation and PTI/DTI ratios — with real-time dealer notifications via SignalR. - Developed and maintained the **Decisioning service's auto-decline rules engine**: rules for bankruptcy, foreclosure, charge-offs and public records, with effective-date-driven rollouts validated against production data. - Integrated **Experian Verify** into the Applicant service for automated income verification, mapping wage types and reducing manual proof-of-income workflows. - Contributed to the redesign of the Partner API Gateway (lead processing, Cognito authentication, document-key queue publishing). - Maintained Launchpad for internal employee process management, including the Originations Tasks manager view. - Led proof-of-concept work evaluating an Angular to React migration, informing the team's frontend modernization strategy. ### CrossBridge Technology Solutions — Senior Software Engineer - Employer: CrossBridge Technology Solutions (consultancy) - Client: Healthcare Finance Direct (patient financing) - Dates: 2019-11 to 2022-05 (2 years 6 months) - Stack: .NET Framework 4.6, .NET Core 2+, ReactJS, SQL Server, PostgreSQL, AWS, Redis, Docker, Kubernetes On the Originations team within a 25–40 person engineering organization, maintaining RESTful APIs consumed by external healthcare providers across a .NET microservices platform and a legacy .NET Framework monolith. - Designed and built the **Underwriting microservice** from initial project stubs through credit matrix rule implementation: evaluating applicant credit history, calculating risk-based interest rates via Enova and CoveredCare integrations, and delivering approval decisions. Built the REST layer, an SQS-based message queue listener, and the integration for third-party credit bureau communication. - Drove the **Finance Offers engine** across three services and built the Providers microservice from scratch (factory pattern, GetOffers and VerifyOffers workflows, Dapper/MSSQL data layer). This moved the platform from generic open financing to provider- and credit-grade-specific offerings, strengthening the Smile Direct Club partnership and laying the foundation for multi-provider onboarding. - Built the **Provider Portal**, a React/TypeScript SPA with Redux and Material UI, to modernize the provider-facing experience: status filtering, API v3 integration and action-button workflows for activation and addendum completion. - Improved the Easy Application patient financing flow end to end: custom down payment support, down payment calculations based on MaxFinanceAmount by credit grade, migration of provider-level waterfall configuration from a database table to feature flags, and SSN masking fixes in e-sign agreements. - Enhanced the Originations API v3 with dynamic multi-field sorting, date-range filtering and applicant name search on the ListApplications endpoint. - Implemented provider validation for the Identity Server migration, support for submitting applications on behalf of child providers, and PreApplication-to-Application ID resolution for the Universal App authentication flow. ### CrossBridge Technology Solutions — Full Stack Developer / Lead Developer - Employer: CrossBridge Technology Solutions (consultancy) - Client: Peerless Maintenance Services - Dates: 2019-05 to 2019-11 - Stack: .NET Core 2+, Angular, Material UI, MySQL, AWS - Gathered requirements directly from the client and designed the full architecture for a custom CRM managing janitorial staff scheduling, shift assignments and work site locations. - Migrated all operational data from legacy Excel records into a structured PostgreSQL database, establishing a reliable foundation for reporting. - Delivered Phase 1, covering core scheduling, staff and location management. ### CrossBridge Technology Solutions — Full Stack Developer / Lead Developer - Employer: CrossBridge Technology Solutions (consultancy) - Client: Assisted Home and Health (home health agency) - Dates: 2018-12 to 2019-05 (concurrent with the StaffTAP engagement) - Stack: .NET Core 2+, Angular, Material UI, MySQL, AWS - Gathered requirements and designed the architecture for a patient management CRM, enabling the agency to maintain structured digital records of patients, medical conditions and individualized care requirements. - Delivered Phase 1 and handed off to a CrossBridge team for continued development. ### CrossBridge Technology Solutions — Full Stack Developer / Lead Developer - Employer: CrossBridge Technology Solutions (consultancy) - Client: StaffTAP - Dates: 2017-01 to 2019-03 (first professional engineering role; overlapped with the Assisted Home and Health and Peerless engagements) - Stack: .NET Framework 4.6, Angular 2, Ionic 2, SQL Server, AWS - Led a three-person development team: gathered client requirements, delegated tasks and managed all production releases. - Rebuilt the legacy web scheduling application from Silverlight to Angular 2, modernizing the UX and eliminating a high-maintenance technology dependency. - Migrated the mobile API from SOAP to RESTful architecture, improving performance and reducing integration complexity for downstream consumers. ## Education - Ingeniería en Sistemas Computacionales (Computer Systems Engineering) — Tecnológico Nacional de México, 2012 to 2016 - Técnico en Informática (Technical Degree in Computing) — Preparatoria #5, UAEM, 2009 to 2012 ## Skills Proficiency levels below are self-assessed. ### Languages - C# — Advanced - TypeScript — Advanced - JavaScript — Advanced - SQL — Intermediate ### Frameworks and libraries - .NET — Advanced - Angular — Advanced - ReactJS — Intermediate - NodeJS — Intermediate Also used in production: NestJS, Blazor, SignalR, Redux, Material UI, Dapper. ### Tools and platforms - Azure — Intermediate - AWS — Intermediate - Git / GitHub — Intermediate - Docker — Beginner Also used: Kubernetes, Redis, RabbitMQ, Pulumi, SQL Server, PostgreSQL, MongoDB, CosmosDB, MySQL, AWS SQS, AWS Cognito. ### AI tools - Claude Code — daily - GitHub Copilot — daily ### Spoken languages - Spanish — Native - English — B2 / C1 ### Ways of working Analytical thinking, requirement gathering, team leadership, written communication, problem solving, adaptable. ## Quantified results - 60,000 new vehicle deals financed in the first two quarters of 2025 (LeadSpy, Prestige Financial Services). - 60% increase in funded deals in the first week after launching the Customer Web App and Interview API (Prestige Financial Services). - Migrated an application across four major framework generations (Angular 6 to 22, .NET Framework 4.6.2 to .NET 10) with complete functional parity (VCA Animal Hospitals). - Clean Architecture structure standardized and adopted across multiple client projects (VCA Animal Hospitals). - Led a three-person development team and owned all production releases (StaffTAP). - Worked within a 25–40 person engineering organization on a .NET microservices platform (Healthcare Finance Direct). ## Seniority Titled Senior Software Engineer since November 2019, across three engagements. Prior to that, Lead Developer on three client projects from January 2017, including leading a three-person team. Experience spans greenfield service design, legacy modernization, rules-engine development, direct client requirement gathering, and mentoring within a mid-size engineering organization.