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EC
Erick Castillo

Lead .Net/Azure Developer

ASP.NET Core REST API Performance Optimization

Hexaware Technologies Lead .NET Developer Oct 2025 - Feb 2026

Challenge:

The ELA platform's REST API had endpoints that performed acceptably under normal traffic but degraded under the spikes the platform sees during active disaster-response windows. Common issues: N+1 query patterns in EF Core, list endpoints returning full entities with every related collection eagerly loaded, async methods that quietly ran synchronously because of a single blocking call, and pagination implemented with Skip/Take against large tables where offset-based paging gets progressively slower. On a federal platform where a traffic spike correlates with the worst possible moment to slow down, the API needed to be tightened before the next event, not after.

Solution:

Profiled and hardened ASP.NET Core REST endpoints across the ELA platform, fixing N+1 query patterns, replacing offset pagination with cursor-based pagination on hot list endpoints, enforcing async-all-the-way-down, and adding response compression and output caching where it was safe. Used MiniProfiler and EF Core query logging to surface the worst offenders, fixed them at the handler and EF Core configuration level rather than papering over with caching, then added caching on top of an already-fast baseline.

Impact:

Hot endpoints stopped degrading under load because the fixes happened at the query and async layers rather than being hidden behind caching. Cursor-based pagination meant deep pages performed as well as shallow ones, which mattered for admin and reporting endpoints that legitimately needed to scroll far into result sets. Async-all-the-way-down freed up request threads under spike traffic, which raised the platform's effective throughput on the same infrastructure. Response compression and output caching layered on top gave additional headroom without masking underlying problems. Structured logging plus Azure Monitor meant the next regression would be easy to find — observability became a real capability, not a checkbox.
C# ASP.NET Core .NET 9 Entity Framework Core Pomelo.EntityFrameworkCore.MySql +10 more
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Erick Castillo

Lead .Net/Azure Developer

Stakeholder Liaison & Cross-Functional Coordination

Hexaware Technologies Lead .NET Developer Mar 2026 - Feb 2026

Challenge:

The ELA platform sat at the intersection of three groups that didn't naturally speak the same language: the federal client (FEMA), Corpay business stakeholders, and cross-functional IT groups including infrastructure, security, and DBA teams. Requirements arrived in business terms, infrastructure changes arrived in ticket-speak, and the development team needed both translated into actionable engineering work without losing fidelity. Misalignment on a federal contract — a misread requirement, a missed compliance constraint, a surprise infrastructure dependency — would have meant rework, blown milestones, or worse. Someone had to own the translation layer so the team could ship.

Solution:

Served as the primary liaison between Corpay business stakeholders, FEMA-facing contacts, and cross-functional IT groups for the full ELA engagement. Coordinated meetings, gathered requirements, surfaced technical constraints early, and translated between business language and engineering language in both directions. Made sure the development team had clear, unambiguous work to do and made sure stakeholders had honest, accurate status — including when something was at risk.

Impact:

Kept the engagement aligned across three groups that had different vocabularies, different incentives, and different definitions of "done." The development team got clear, unambiguous work because requirements were translated and validated before they hit the backlog. Stakeholders got honest status, including when something was at risk, which built trust faster than optimistic reporting would have. Cross-functional dependencies (infrastructure, DBA, security) were surfaced early enough to schedule around rather than absorb as surprises. The documentation trail — meeting scripts, ADRs, Jira tickets — gave the engagement a defensible record on a federal contract where audit-readiness matters.
Jira GitLab Markdown TDDs and ADRs meeting scripts stakeholder status documents +3 more
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EC
Erick Castillo

Lead .Net/Azure Developer

Team Leadership & Knowledge Transfer Program

Hexaware Technologies Lead .NET Developer Oct 2025 - Feb 2026

Challenge:

The ELA platform's five-developer team came in with mixed experience levels and uneven exposure to the codebase, Clean Architecture conventions, and the modern .NET stack the platform was moving toward. On a federal contract with hard milestones, the team couldn't afford a slow, sink-or-swim onboarding curve — knowledge had to transfer fast, and it had to stick. Beyond onboarding, there was no shared rhythm for code review, no consistent forum for surfacing tricky architectural decisions, and no defensible record that mentorship was actually happening. Skills gaps left unaddressed would have shown up later as production defects on a 24/7 government-facing platform.

Solution:

Built and ran a structured knowledge-transfer and mentorship program for the five-developer team covering KT sessions, mob-coding exercises, and code reviews as deliberate teaching moments rather than just gates. Made skill development a tracked part of the engagement rather than a side effect, and used the program to enforce Clean Architecture, CQRS, and the team's AI-native engineering standards consistently across the team.

Impact:

Built a team that could ship Clean Architecture .NET features at a consistent quality bar rather than a per-developer one. KT sessions and mob-coding gave the team a shared mental model of the ELA platform, which cut down on architecture-drift comments in code review and made onboarding new tickets faster. Code review shifted from gatekeeping to teaching, which raised the floor on code quality without slowing throughput. The rotation of session leadership built bench depth — more than one person could explain any given subsystem — which mattered on a federal platform where bus-factor risk was real. Mentorship deliverables (AI-native workflow, spec-first practice) gave team members skills that ported beyond the engagement.
ASP.NET Core .NET 9 C# Clean Architecture CQRS / MediatR +7 more
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Erick Castillo

Lead .Net/Azure Developer

AI-Native Engineering Standards Rollout

Hexaware Technologies Lead .NET Developer Oct 2025 - Dec 2025

Challenge:

The five-person ELA development team was shipping .NET features at a traditional pace — handwritten CQRS handlers, manually scaffolded EF Core configurations, and inconsistent test coverage across modules. AI tools were available to the organization but used inconsistently: some developers leaned on Copilot for autocomplete, others ignored it entirely, and no one had a shared convention for prompts, context, or AI-assisted code review. The result was uneven velocity, duplicated effort across the team, and no defensible way to measure whether AI tooling was actually helping. On a federal contract with hard delivery milestones, the team needed a repeatable workflow rather than ad-hoc AI use.

Solution:

Defined and rolled out team-wide AI-native engineering standards covering spec-first development, prompt and context conventions, and AI-augmented code review checkpoints. Integrated Claude Code, GitHub Copilot, and M365 Copilot into the daily workflow with clear guardrails on what each tool was best for. Established markdown-based Technical Design Documents as the single source of truth that AI agents would consume to scaffold new modules, then trained the team on the workflow through mob-coding sessions and code reviews.

Impact:

Shifted the team from ad-hoc AI use to a defined, repeatable workflow with shared conventions and review gates. Time-to-first-working-build for new modules dropped meaningfully once TDD-driven scaffolding became the default — handlers, EF Core configs, and tests generated from spec instead of typed by hand. Code review quality improved because reviewers had a clear checklist for AI-generated code, and onboarding got faster because the standards doc and CLAUDE.md context files gave new developers a runway. The team built a defensible story for leadership that AI tooling wasn't just autocomplete — it was a productivity multiplier with measurable gates.
Claude Code (Anthropic) GitHub Copilot M365 Copilot ASP.NET Core .NET 9 +9 more
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EC
Erick Castillo

Lead .Net/Azure Developer

MySQL 5.7 → 8.0 Migration & HA Failover Validation

Hexaware Technologies Lead .Net Developer Oct 2025 - Feb 2026

Challenge:

The FEMA ELA platform's primary data store ran on MySQL 5.7, which was approaching end-of-life and lacked the security, performance, and JSON/CTE features the .NET application increasingly relied on. On a federal platform supporting emergency lodging during disaster events, the database also had to demonstrate verified high-availability failover — a documented, repeatable test, not a hope. Upgrading in place risked breaking EF Core data access, stored procedures, and existing query plans, and a botched failover during an active disaster response would have been a serious incident.

Solution:

Owned the MySQL 5.7 → 8.0 upgrade plan end-to-end and ran the HA failover validation exercise alongside it. Authored the TDD covering compatibility analysis, upgrade path, rollback strategy, and the failover test protocol. Coordinated with Corpay infrastructure, the FEMA stakeholders, and the dev team to schedule the cutover, then executed and signed off on the failover drill against the upgraded cluster.

Impact:

Brought the ELA platform onto a supported MySQL version with stronger security defaults and modern SQL features, eliminating EOL risk on a federal contract. The HA failover drill produced a signed-off, repeatable runbook — meaning the on-call team had verified evidence of failover behavior rather than a theoretical design. EF Core data access continued working without regressions across the full integration test suite, and the Azure Blob backup pipeline gave the platform a clean DR posture going into disaster season.
MySQL 5.7 MySQL 8.0 MySQL Shell ASP.NET Core .NET 9 +7 more
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Jason Assistant

Mission Control Automation & Productivity Upgrade

UXL Solutions LLC Senior .NET Developer Feb 2026 - Present

Challenge:

The team lacked a centralized operational view for AI agent execution, task progress, and business intelligence updates. This created delays in decision-making, weak visibility into active work, and inconsistent follow-through on high-priority initiatives.

Solution:

Built a Mission Control dashboard and workflow automation layer to centralize task orchestration, activity tracking, and proactive reporting. Added automated intelligence feed generation and reliability checks to ensure critical updates are available daily.

Impact:

Created a single source of operational truth for daily execution. Leadership now gets faster visibility into what is in progress, what is blocked, and what to prioritize next, enabling higher execution speed and better resource allocation.
ASP.NET Core C# JavaScript Node.js Redis +2 more
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EC
Erick Castillo

Lead .Net/Azure Developer

Financial Reporting Platform & Lease Accounting Automation

LeaseQuery .Net Developer Dec 2018 - Mar 2019

Challenge:

Financial institutions and enterprises needed compliant lease accounting solutions to meet GAAP standards. Manual data processing between systems was time-consuming and error-prone, and the existing application lacked real-time data capabilities and code reusability, hindering development velocity.

Solution:

Developed custom financial reporting solutions using ASP.NET Core with React and Angular frontends for lease accounting automation. Built complex SQL queries and stored procedures for compliance reporting. Integrated third-party APIs for automated data synchronization. Implemented component-based architecture with RESTful APIs and Vue.js for real-time data updates

Impact:

Delivered audit-ready financial compliance reporting supporting GAAP standards. Reduced manual data processing time by 50% through automated third-party API integrations. Improved code reusability and scalability through component-based architecture. Enabled real-time data updates for faster decision-making.
.Net SQL API
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EC
Erick Castillo

Lead .Net/Azure Developer

Enterprise Testing Framework & Quality Assurance Automation

Atos Syntel .Net Developer Jul 2020 - Oct 2020

Challenge:

The organization managed 100+ applications with inconsistent testing practices, low code coverage, and high bug escape rates. Bug detection was slow, quality assurance was largely manual, and application performance suffered from unoptimized code paths, resulting in slow response times on critical endpoints.

Solution:

Developed a comprehensive unit testing framework using MSTest and NUnit to standardize testing across the enterprise. Implemented automated testing strategies integrated with CI/CD pipelines. Performed code optimization and profiling to improve application performance across critical endpoints.

Impact:

Achieved 85%+ code coverage across the enterprise application portfolio. Reduced bug detection time by 60%, significantly improving software quality. Improved response times by 35% on critical application endpoints. Accelerated release cycles through automated testing and reliable deployment processes.
.Net SQL Azure DevOps
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Erick Castillo

Lead .Net/Azure Developer

Cloud-Native Retail Platform & Azure Cost Optimization

Meijer .Net Developer May 2021 - Jul 2021

Challenge:

Mission-critical retail operations spanning 200+ stores required high-availability systems capable of processing 100K+ daily transactions. The existing infrastructure had high cloud costs, lacked Infrastructure as Code practices, and suffered from data latency issues across distributed environments. Junior developers needed upskilling on cloud architecture patterns.

Solution:

Developed cloud-native applications using Azure Functions, Service Bus, and Event Grid for reliable message-driven architecture. Integrated CosmosDB for high-throughput, geo-redundant data operations. Implemented CI/CD pipelines with Infrastructure as Code (ARM templates). Executed Azure cost optimization strategies and built reporting solutions with Power BI. Mentored junior developers on cloud best practices.

Impact:

Achieved 25% reduction in Azure infrastructure costs through optimization strategies. Ensured high availability and performance at scale for 200+ retail stores. Enabled low-latency data access across distributed environments with CosmosDB. Reduced manual release overhead through automated deployments and Infrastructure as Code. Accelerated team capability growth through mentorship on cloud architecture.
.Net SQL Azure Cosmos DB Service Bus
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Erick Castillo

Lead .Net/Azure Developer

Microservices Architecture & Cloud Platform Modernization

RMCI .Net Developer May 2023 - Nov 2023

Challenge:

The existing monolithic .NET Framework 4.8 application struggled to scale under growing user demand (10,000+ daily users), suffered from tightly coupled components that slowed feature delivery, and lacked proper API governance. Issue detection was slow and reactive, leading to extended downtime and poor user experience.

Solution:

Redesigned the application architecture from monolithic to microservices using Docker and Azure Kubernetes Service (AKS). Migrated legacy .NET Framework 4.8 applications to .NET Core and integrated Java microservices. Implemented Azure API Management for centralized API governance and Azure Monitor with Application Insights for proactive performance monitoring. Built serverless event-driven applications using Azure Functions.

Impact:

Improved system scalability by 40% and enabled independent service deployments. Boosted application performance by 30% through the .NET Core migration. Reduced issue detection time by 50% and maintained 99.9% application uptime. Reduced infrastructure overhead through serverless architecture. Improved API governance and security across the platform.
.Net Azure SQL APIM API +1 more
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