Claude Code
api
CORS Preflight Request Failing
Frontend makes a complex request (POST with JSON body) to API, preflight OPTIONS request fails with 403 or 405 error. Actual request never sent because browser stops at preflight check. Simple GET requests work but POST/PUT/DELETE fail.
CORS configuration exists but doesn't handle preflight requests correctly.
Error Messages You Might See
Error: Request blocked by CORS policy
Preflight response has invalid HTTP status code 403
Method not allowed in CORS preflight
Common Causes
- OPTIONS method not allowed in CORS configuration
- CORS headers missing or misconfigured: Access-Control-Allow-Methods
- Custom headers not whitelisted: Access-Control-Allow-Headers
- Credentials not allowed: Access-Control-Allow-Credentials missing
- Origin not in allowed list for preflight
How to Fix It
Ensure OPTIONS requests are handled and return 200 with CORS headers. Configure: Access-Control-Allow-Methods: GET, POST, PUT, DELETE, OPTIONS. Access-Control-Allow-Headers: Content-Type, Authorization. Access-Control-Allow-Origin: * (or specific domain). Access-Control-Allow-Credentials: true (only if credentials needed). Test preflight: curl -i -X OPTIONS http://api.example.com/endpoint
Real developers can help you.
PawelPloszaj
I'm fronted developer with 10+ years of experience with big projects. I have small backend background too
Daniel Vázquez
Software Engineer with over 10 years of experience on Startups, Government, big tech industry & consulting.
Jacek Rozanski
Senior PHP/Symfony developer and DevOps engineer with 20+ years of professional experience, running opcode.pl (web development agency, est. 2004).
Day job: I'm the sole backend developer at merketing company where I own and maintain 11 PHP/Symfony microservices on AWS (ECS Fargate, RDS, S3, CloudFront), handle the full CI/CD pipeline (Bitbucket Pipelines, Docker), and manage monitoring with Sentry and CloudWatch. These services handle high request volumes in production every month.
What I bring to AI-built apps:
- I audit and fix security issues (OWASP methodology), performance bottlenecks, and architectural problems in codebases generated by Cursor, Claude Code, Lovable, Bolt, and v0
- I refactor AI-generated prototypes into production-grade applications with proper error handling, testing, and clean architecture (SOLID, DDD, hexagonal architecture)
- I set up the infrastructure AI tools don't touch: AWS hosting, CI/CD pipelines, automated deployments, database optimization, monitoring, and alerting
- I integrate external services: payment providers, email systems, partner APIs, SSO/auth
Tech stack: PHP 8.x, Symfony, React, Next.js, PostgreSQL, MySQL, Docker, AWS (ECS, RDS, S3, SQS/SNS, CloudFront), Terraform, Supabase. I also use AI tools daily (Claude Code, Cursor) in my own workflow, so I understand both the strengths and the gaps in AI-generated code.
Based in Poland (CET timezone). Available for async work and calls during EU/US business hours.
Jen Jacobsen
I’m a Full-Stack Developer with over 10 years of experience building modern web and mobile applications. I enjoy working across the full product lifecycle — turning ideas into real, well-built products that are intuitive for users and scalable for businesses.
I particularly enjoy building mobile apps, modern web platforms, and solving complex technical problems in a way that keeps systems clean, reliable, and easy to maintain.
Victor Denisov
Developer
Alvin Voo
I’ve watched the tech landscape evolve over the last decade—from the structured days of Java Server Pages to the current "wild west" of Agentic-driven development. While AI can "vibe" a frontend into existence, I specialize in the architecture that keeps it from collapsing.
My expertise lies in the critical backend infrastructure: the parts that must be fast, secure, and scalable. I thrive on high-pressure environments, such as when I had only three weeks to architect and launch an Ethereum redemption system with minimal prior crypto knowledge, turning it into a major revenue stream.
What I bring to your project:
Forensic Debugging: I don't just "patch" bugs; I use tools like Datadog and Explain Analyzers to map out bottlenecks and resolve root causes—like significantly reducing memory usage by optimizing complex DB joins.
Full-Stack Context: Deep experience in Node.js and React, ensuring backends play perfectly with mobile and web teams.
Sanity in the Age of AI: I bridge the gap between "best practices" and modern speed, ensuring your project isn't just built fast, but built to last.
Dor Yaloz
SW engineer with 6+ years of experience,
I worked with React/Node/Python
did projects with React+Capacitor.js for ios
Supabase expert
hanson1014
Full-stack developer experienced in fixing and deploying AI-generated apps from Lovable, Bolt.new, Cursor, and Replit. I specialize in debugging Supabase integration issues (auth flows, RLS policies, database connections), fixing broken deployments, resolving routing/blank screen problems, and cleaning up messy React/Vite codebases. I also build production apps with the Claude API and have shipped a Mac desktop dev tool (Nexterm from scratch. Based in Hong Kong, fast turnaround.
Sage Fulcher
Hey I'm Sage! Im a Boston area software engineer who grew up in South Florida. Ive worked at a ton of cool places like a telehealth kidney care startup that took part in a billion dollar merger (Cricket health/Interwell health), a boutique design agency where I got to work on a ton of exciting startups including a photography education app, a collegiate Esports league and more (Philosophie), a data analytics as a service startup in Cambridge (MA) as well as at Phillips and MIT Lincoln Lab where I designed and developed novel network security visualizations and analytics. I've been writing code and furiously devoted to using computers to make people’s lives easier for about 17 years. My degree is in making computers make pretty lights and sounds. Outside of work I love hip hop, the Celtics, professional wrestling, magic the gathering, photography, drumming, and guitars (both making and playing them)
Matt Butler
Software Engineer @ AWS
You don't need to be technical. Just describe what's wrong and a verified developer will handle the rest.
Get HelpFrequently Asked Questions
What is CORS preflight?
For non-simple requests (POST with JSON, custom headers), browser sends OPTIONS first to check if request allowed. If OPTIONS fails, actual request never sent.
How to allow all origins?
Access-Control-Allow-Origin: * allows all. For credentials, use specific domain: Access-Control-Allow-Origin: https://example.com
What headers must be allowed?
At minimum: Content-Type. Also: Authorization if using tokens. Declare with: Access-Control-Allow-Headers: Content-Type, Authorization