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Remote | Contract / Contract-to-Hire | Senior Level We're looking for a highly experienced Full-Stack Engineer / Software Architect to help transform an existing SaaS platform into a scalable, configuration-driven, AI-ready system. This is not a greenfield build. We already have a working Java-based MVP and need someone who can modernize and simplify the architecture while preserving existing functionality. The Project Our platform combines: Organizational analytics Scoring & indicator frameworks Surveys and behavioral signals AI-assisted recommendations Workflow automation The current system works, but much of the business logic is hardcoded. We need a senior engineer who can redesign the architecture to become more configurable, scalable, and maintainable. Key Responsibilities Architecture Refactoring Convert hardcoded scoring and indicator logic into configuration-driven models Design versioned business rules and indicator definitions Improve service boundaries and system maintainability Refactor without rewriting the entire platform Data & Analytics Design a unified signal ingestion framework Normalize survey, KPI, workflow, and future AI-generated signals Build scalable scoring and aggregation services Optimize PostgreSQL data models and analytics workflows AI Enablement Implement AI-generated insights and recommendations Design human-in-the-loop approval workflows Create auditable and controlled AI execution patterns Engineering Productivity Simplify code and reduce technical debt Improve scalability and performance Leverage AI development tools to accelerate delivery Required Experience Must Have 5+ years building SaaS applications Strong backend and system architecture experience PostgreSQL / relational database expertise REST API design and development Multi-tenant SaaS architecture experience Experience refactoring existing systems Ability to work independently and own technical decisions Preferred Java experience Node.js or Python experience Event-driven architectures Rules engines, scoring engines, or analytics platforms Production AI feature development Heavy use of Cursor, Claude, Copilot, Windsurf, or similar AI tools Ideal Candidate You: Think in systems, not individual features Simplify rather than over-engineer Understand startup speed and constraints Can make architectural decisions with minimal oversight Have successfully modernized existing SaaS platforms To Apply Please send: GitHub, LinkedIn, or Portfolio A brief example of a system you refactored or modernized Your preferred tech stack AI development tools you actively use Availability and hourly/monthly rate Bonus: Include a short paragraph describing how you would approach converting hardcoded business logic into a configuration-driven platform.
Project ID: 40528944
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43 freelancers are bidding on average $3,864 USD for this job

With over a decade of experience in full-stack architecture and high-scale systems, I understand the critical need to transform your existing SaaS platform into a more scalable, AI-ready system. Your project goal of refactoring the architecture to be configurable and maintainable aligns perfectly with my background in scaling systems for over 1 million users and optimizing high-security FinTech platforms. A strategic insight for your project is to implement versioned business rules and indicator definitions to ensure flexibility and scalability in the long term. In a past project, I successfully built and scaled a Telegram Mini App serving over 1 million users, showcasing my ability to handle complex systems like the one your project requires. I encourage you to reach out to me to discuss the roadmap for transforming your platform. I am confident that my expertise in AI development, system architecture, and refactoring existing systems make me the ideal candidate to help realize your project goals. Let's connect and explore how we can drive your platform towards greater success.
$4,000 USD in 45 days
7.7
7.7

Hi, I’m excited about the opportunity to help modernize your SaaS platform. With over 6 years of experience building and refactoring multi-tenant SaaS systems, I’ve successfully transitioned legacy architectures into scalable, configuration-driven solutions. My backend expertise spans Java, Python, and Node.js, with a strong focus on PostgreSQL optimization and REST API design. I’ve worked on evolving hardcoded business rules into flexible, versioned models, enabling easier updates and better maintainability. I prioritize simplifying complex systems without over-engineering, aligning well with your goal to improve system agility and performance. I also leverage AI tools like Copilot and Windsurf to accelerate development, especially for AI-generated insights and automation workflows. My portfolio includes refactoring legacy analytics engines into modern, scalable architectures that support AI integration and enhance user experience. I am confident I can help redesign your platform’s architecture to be more configurable, scalable, and future-proof while preserving core functionality. Best, Justin
$4,000 USD in 7 days
6.6
6.6

Hello, Your SaaS platform mixes organizational analytics, scoring frameworks, surveys, behavioral signals and AI‑driven recommendations into workflow automation. The goal is to replace hard‑coded scoring/indicator logic with a version‑controlled, configuration‑driven model, unify signal ingestion, and add auditable AI insights with human‑in‑the‑loop approval while preserving existing functions. Technical approach: Use a modular Spring Boot (Java) backend with a pluggable rule engine (JSON schema/Drools) for configurable scoring, per‑tenant PostgreSQL schemas, event‑driven ingestion (RabbitMQ/Kafka) to normalize survey, KPI, workflow and AI signals, REST/GraphQL APIs, and an AI service layer built on LangChain/LLM endpoints wrapped in approval workflows. Feature flags and Docker‑based CI/CD allow safe incremental rollout. Core modules: Rule Configuration Service, Signal Ingestion & Normalization Service, Scoring & Aggregation Engine, AI Insight Service with Human‑Loop Approval, Admin Console for tenant config/versioning, Audit & Versioning Service. Relevant systems: Bison360 (Spring Boot, React, Flutter, PostgreSQL) - refactored legacy to modular SaaS; RecurGo (Spring Boot, React, Flutter, PostgreSQL/MongoDB) - AI‑powered matching with config‑driven pipelines; TDTY (Node.js, React, AWS) - event‑driven, multi‑tenant content platform. Implementation strategy: 1) externalize hard‑coded rules into config and build Rule Service; 2) create unified signal ingestion API and normalization workers; 3) develop scoring microservice using the rule engine; 4) add AI insight layer with approval workflows; 5) roll out via feature flags, load test and tune performance; 6) final cut‑over and documentation. Questions: 1) Expected peak throughput (events/sec) for signal ingestion after refactor? 2) Preferred rule‑engine (Drools, JSON Schema, custom) or should we evaluate options? 3) How critical is sub‑second AI recommendation latency versus batch processing for your analytics? Regards, Rohit
$3,000 USD in 45 days
5.9
5.9

As the name implies, I have a proclivity towards turning outdated systems into streamlined, sophisticated solutions that amplify business efficiency. Over the course of my 7+ years; overhauling SaaS platforms has become one of my fortes. I understand the importance of technological scalability and simplification. That's why I've mastered tools like PostgreSQL, REST API along with Java, Node.js and Python. These skills enable me to translate your complex, hardcoded scoring and indicator logic into an easy-to-manipulate configuration-driven model that will empower your platform to not just accommodate AI integration but also make the management process so much smoother. In addition to transforming platforms like yours, I also excel in designing unified signal ingestion frameworks, normalizing various types of signals such as surveying KPIs or workflow data and building scalable scoring/aggregation services. My talent extends beyond data management too; I possess a unique acumen for AI feature development which involves developing AI-generated insight and recommendations. Another skill worth noting is my ability to simplify codebase without underestimating its functionalities, improving both scalability and performance - an aspect that’s rather important for a future-leaning transformation like yours.
$4,000 USD in 30 days
5.3
5.3

The hidden risk in refactoring hardcoded scoring logic is that versioned business rules can silently diverge, causing legacy analytics to produce mismatched results after a deploy. I cut deployment time by 42% on a multitenant SaaS by extracting rule definitions into JSON schemas and automating migration tests, keeping data integrity across releases. First 24hours I would audit the existing Java MVPs rule engine, extract all hardcoded thresholds into a versioncontrolled repository, and write integration tests that compare current outputs to the new configurable modelensuring no regression before any code moves. Quick questionare the current scoring formulas stored exclusively in Java enums, or do you also have them embedded in SQL procedures? That determines the migration path. - Abdullah Z. (@redspector) | CEH | OSCP | AWS | Docker
$4,500 USD in 25 days
5.1
5.1

Hello, I am a senior Full-Stack Developer with 8+ years of experience building and modernizing scalable SaaS platforms. I have strong expertise in system architecture, Java, Spring Boot, REST APIs, PostgreSQL, multi-tenant applications, and refactoring complex legacy systems into maintainable, configuration-driven architectures. I can help transform your existing MVP by eliminating hardcoded business logic, designing scalable rule-based frameworks, optimizing data models, and enabling AI-ready workflows while preserving current functionality. I am comfortable owning technical decisions, reducing technical debt, and delivering scalable, production-grade solutions. I would be glad to discuss your platform and architectural goals in detail. Regards
$4,000 USD in 7 days
5.3
5.3

⭐⭐⭐⭐⭐ Transform Your SaaS Platform with a Senior Full-Stack Engineer ❇️ Hi My Friend, I hope you're doing well. I’ve reviewed your project needs and see you are looking for a Full-Stack Engineer to modernize your SaaS platform. Look no further; Zohaib is here to assist you! My team has successfully completed 50+ similar projects for SaaS platforms. I will focus on simplifying the architecture while keeping the existing functionality intact, ensuring a smooth transition. ➡️ Why Me? I have over 5 years of experience in building SaaS applications, focusing on backend development and system architecture. My skills include PostgreSQL optimization, REST API design, and multi-tenant architectures. I excel in refactoring existing systems and can make independent technical decisions to enhance your platform. ➡️ Let's have a quick chat to discuss your project in detail and let me show you examples of my previous work. I look forward to our discussion! ➡️ Skills & Experience: ✅ SaaS Development ✅ Backend Architecture ✅ PostgreSQL Expertise ✅ REST API Development ✅ Multi-Tenant Systems ✅ System Refactoring ✅ AI Integration ✅ Data Normalization ✅ Workflow Automation ✅ Code Optimization ✅ Performance Improvement ✅ Technical Decision Making Waiting for your response! Best Regards, Zohaib
$3,400 USD in 2 days
5.4
5.4

Hi, I've read your brief — a senior AI-native full-stack engineer for a SaaS. This is squarely our wheelhouse at Global IT Vision (AI-first SaaS; our FOXAF CRM is AI-native). My approach: - Full-stack delivery (modern frontend + backend APIs) with AI woven in natively — LLM features, RAG, agents/pipelines — not bolted on. - Clean architecture, tests, and scalable, secure infra. - Reliable senior contribution + clear communication. I've posted scope questions on the board. Could we do a quick call to learn the stack + the AI features? — Muhammad Idrees / Global IT Vision Pvt. Ltd
$3,000 USD in 30 days
4.9
4.9

With over a decade of experience transforming existing platforms, I am confident that my technical acumen aligns perfectly with your project requirements. Having delivered 416 successful projects, I have earned a reputation for building scalable and maintainable platforms from the ground up. In particular, I specialize in refactoring systems to make them more efficient, which is precisely what you need. I have a strong command in several backend languages including Java and programming languages like Node.js and Python that could be useful while transcending the business logic to a configuration-driven environment. Benefiting startups has always been my forte where speed and constraints rule the roost. Therefore, I understand the exact needs of an organization like yours and assure you that my agile and swift problem-solving skills aligns aptly with pivotal decision-making required to handle this project efficiently. I believe that - system simplification is key while refactoring complex endpoints - something we both emphasize. In conclusion, Arun's team offers you not only guided innovations in Full Stack engineering but an ally that can guarantee your platform stands out online amidst fierce competition. Let's connect and explore how we can actualize all the exciting potential of your SaaS system together!
$4,500 USD in 20 days
4.5
4.5

Hi, This is squarely the kind of work I focus on—modernizing existing SaaS platforms into configurable, scalable systems without throwing away what already works. Your brief reads like a refactor, not a rewrite, and that's exactly how I'd approach it: preserve functionality, improve service boundaries, and convert hardcoded logic into versioned, configuration-driven models incrementally. On architecture, I'd lift the scoring and indicator logic out of code into versioned rule/indicator definitions (stored and validated in PostgreSQL), so business rules become data you can change and audit rather than deployments. For data, I'd design a unified signal ingestion framework that normalizes surveys, KPIs, workflow events, and future AI signals into a common model feeding scalable scoring and aggregation services. For AI enablement, I'd build human-in-the-loop approval and auditable, controlled execution patterns so AI recommendations stay reviewable and safe. **Stack:** Java/Spring on the existing base, PostgreSQL, REST, with Node or Python where it fits. I lean heavily on Claude and Cursor day to day to accelerate delivery without sacrificing quality. To answer your question: the tightest hardcoding is usually scoring rules and indicator definitions, so I'd start there—extracting them behind a rules/scoring engine with backward compatibility maintained throughout, page by page, never a big-bang cutover
$3,000 USD in 70 days
3.6
3.6

Krishna here from delhi. As a dedicated software development team, our strength lies in transforming existing platforms into adaptable, scalable and high-performing systems. And that is precisely why I believe our expertise as AI-native full-stack engineers aligns perfectly with your project requirements. Over the past five years, we've honed our skills in SaaS application building, backend architecture, and PostgreSQL which makes us well-versed in the task of modernizing and simplifying your Java-based MVP. What sets us apart is our ability to create complex systems that are configurable and maintainable. We approach every project with the intention of long-term success; thus simplifying the codebase, reducing technical debt, improving scalability/performance, are all strategies that we employ to ensure a solid foundation for growth. As AI specialists, we can integrate AI-generated insights into your system to make it more intelligent and efficient than ever before while maintaining essential human-in-the-loop approval workflows for absolute control. Furthermore, being familiar with many popular AI development tools like those you've mentioned such as Cursor and Copilot to name a few, we can leverage these tools to accelerate delivery for your organization without compromising quality or efficiency.
$4,000 USD in 7 days
3.6
3.6

I bring strong experience in SaaS architecture modernization, scalable backend design, and converting tightly coupled business logic into configuration-driven systems without disrupting existing functionality. I can help refactor your Java MVP into a maintainable, multi-tenant, AI-ready platform with cleaner service boundaries, scalable scoring frameworks, optimized PostgreSQL models, and a practical roadmap that balances startup speed with long-term scalability.
$4,000 USD in 7 days
3.0
3.0

Hello, I see you need a senior engineer to refactor your existing SaaS platform. I'm Mubashir, a Full-Stack Developer with 6+ years of experience in modernizing SaaS applications. Deliverables: - Scalable and configuration-driven system - Hardcoded business logic converted into configurable models PROCESS: - Analyze current Java-based MVP, identify hardcoded logic and document required changes. - Design new architecture with versioned business rules and indicator definitions. - Create unified signal ingestion framework for normalized data types and improved PostgreSQL data models and analytics workflows. - Implement AI-generated insights and human-in-the-loop approvals. - Simplify existing codebase, reducing technical debt and optimizing performance and scalability. My Portfolio: https://www.freelancer.com/u/mubashir021 I'd be happy to provide a FREE detailed quotation and project proposal with a suggested roadmap.
$3,950 USD in 10 days
2.5
2.5

I understand you need a Senior AI-Native Full-Stack Engineer to refactor your existing Java-based SaaS platform, focusing on organizational analytics, scoring, surveys, and AI-assisted recommendations, transforming it into a configuration-driven, AI-ready system without a greenfield build. I successfully architected and implemented a similar modernization for a client, resulting in a 30% reduction in operational costs and a 2x increase in feature deployment speed. I will deliver a modernized architecture using a microservices approach, with APIs built in Python (FastAPI) and a PostgreSQL database. The front-end will be rebuilt in React, leveraging a component-based system for reusability. Configuration will be managed via a dedicated service, and AI models will be integrated through standardized interfaces. I'll ensure all existing functionality is preserved and accessible through the new architecture. What specific tooling or frameworks are currently in place for the AI-assisted recommendations component that you'd like to see preserved or integrated into the new architecture? Ready to start as soon as you confirm scope.
$3,000 USD in 21 days
1.4
1.4

Hello, Your project aligns well with my experience in SaaS architecture, AI-powered platforms, and system modernization. I have extensive experience building and refactoring scalable applications using Java, Node.js, Python, PostgreSQL, REST APIs, and multi-tenant architectures. Rather than rewriting the platform, I would focus on extracting hardcoded business logic into configuration-driven models, versioned rules, and reusable scoring frameworks while preserving existing functionality and minimizing risk. My approach would be to create a centralized configuration layer for indicators, scoring rules, thresholds, and workflows stored in mangoDb, allowing business users to evolve logic without code changes. I would also design a unified signal ingestion framework, scalable analytics services, AI-assisted recommendation workflows with human approval controls, and clear service boundaries to reduce technical debt and improve maintainability. I actively use Cursor, Claude, GitHub Copilot, and OpenAI tools to accelerate development, documentation, testing, and refactoring. I can work independently, make architecture decisions, and deliver practical solutions that balance startup speed with long-term scalability. I would be happy to discuss your current architecture, modernization roadmap, availability, and engagement structure.
$5,000 USD in 20 days
1.6
1.6

Hi, I specialize in transforming SaaS platforms into scalable, AI-ready systems. With over 15 years of experience in software development and a strong background in architecture refactoring, I’ve successfully modernized various platforms while preserving core functionalities. My approach for your project includes: 1. Auditing the existing Java-based MVP to identify hardcoded logic and areas for improvement. 2. Designing configurable models for scoring and indicators to enhance flexibility. 3. Establishing a signal ingestion framework to streamline data normalization and analytics. 4. Optimizing PostgreSQL data models tailored for scalability and efficient AI integration. I actively use development tools that expedite AI solutions and have experience with Node.js and Python which will be beneficial for your refactoring needs. For a project of this nature, I propose a budget of $4500 for a comprehensive solution over approximately 60 days. This quote reflects the complexity and the need for high-quality architecture. Let’s discuss this in detail. I look forward to hearing from you soon. Regards, Anil Kamani
$4,500 USD in 60 days
0.0
0.0

Hi, I read through your project for Senior AI-Native Full-Stack Engineer (SaaS Architecture & Platform Refactoring) (Bahrain Based Mandatory). You need help with senior ai-native full-stack engineer (saas architecture & platform refactoring) (bahrain based mandatory). I can build and deliver this efficiently based on the job requirements. This fits well with my experience in AI Content Creation. I can take what you outlined and turn it into a clean final delivery, with attention to AI Content Creation and the details in your brief. I will keep the implementation clean, practical, and aligned with your requested scope. Send me the details and I can start immediately.
$3,000 USD in 1 day
0.0
0.0

Thank you for considering my application! As an accomplished full-stack engineer with over 5 years of experience in building and refining SaaS applications, I am confident that I possess the necessary skill set to execute this project perfectly. My knowledge in Java, Node.js, Python, and deep understanding of PostgreSQL and REST API design will aid me greatly in modernizing your existing SaaS platform while preserving its functionality. I specialize in simplifying complex systems and making them more configurable and maintainable, which aligns perfectly with your needs. One of my key strengths is my ability to identify and resolve technical debt while ensuring backend optimization and performance improvement. In addition, I have extensively worked on AI deployment and scoring engines during my tenure as a full-stack engineer. I believe this experience makes me well-suited for implementing AI-generated insights in your system as laid out in your project description. Lastly, as a freelancer who values self-reliance, I can assure you that I'll be able to efficiently work on and make sound technical decisions for your project with minimal oversight. If selected, my immediate focus will be to convert the hardcoded scoring and indicator logic into configuration-driven models while improving scalabilty and maintainability of the system as a whole. My availability is open and my rate reflects the proficiency you can expect from me.
$3,500 USD in 7 days
0.0
0.0

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