Claude Code
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Race Conditions Causing Data Corruption on Concurrent Updates
When multiple users or processes update the same data simultaneously, your application produces incorrect results. Inventory counts go negative, account balances are wrong, duplicate records appear, or the last write silently overwrites earlier changes without merging them.
Race conditions are among the hardest bugs to find because they're non-deterministic. They happen occasionally under load but almost never during manual testing. You might only discover them when a user complains that their changes disappeared, or when financial totals don't add up.
Claude Code generates code that works correctly for sequential operations but doesn't add concurrency controls. Every read-modify-write sequence without locking is a potential race condition waiting to be triggered under production load.
Error Messages You Might See
ERROR: could not serialize access due to concurrent update
OptimisticLockException: Row was updated by another transaction
Inventory cannot be negative: constraint violation
Duplicate entry for key 'unique_order_id'
StaleObjectStateError: Row was updated or deleted
Common Causes
- Read-modify-write without locking — Code reads a value, modifies it in application code, and writes it back. Between read and write, another request changes the value
- Missing database transactions — Multiple related operations are not wrapped in a transaction, allowing partial completion
- Optimistic concurrency not implemented — No version column or ETag to detect and reject conflicting writes
- Shared mutable state — In-memory counters, caches, or rate limiters modified by multiple async operations without synchronization
- Idempotency not enforced — Retry logic or duplicate requests cause the same operation to execute multiple times
How to Fix It
- Use atomic database operations — Replace read-modify-write with UPDATE counters SET value = value + 1 WHERE id = X
- Add optimistic locking — Include a version column and use UPDATE ... WHERE version = expected_version. Retry on conflict
- Wrap operations in transactions — Use database transactions with appropriate isolation levels (READ COMMITTED or SERIALIZABLE)
- Implement idempotency keys — Accept a client-generated idempotency key and skip duplicate operations
- Use distributed locks for critical sections — For operations spanning multiple services, use Redis-based distributed locks (Redlock)
- Test with concurrent load — Use tools like k6 or Artillery to send concurrent requests and verify data integrity
Real developers can help you.
Omar Faruk
As a Product Engineer at Klasio, I contributed to end-to-end product development, focusing on scalability, performance, and user experience.
My work spanned building and refining core features, developing dynamic website templates, integrating secure and reliable payment gateways, and optimizing the overall system architecture.
I played a key role in creating a scalable and maintainable platform to support educators and learners globally.
I'm enthusiastic about embracing new challenges and making meaningful contributions.
Mehdi Ben Haddou
- Founder of Chessigma (1M+ users) & many small projects
- ex Founding Engineer @Uplane (YC F25)
- ex Software Engineer @Amazon and @Booking.com
Rudra Bhikadiya
I build and fix web apps across Next.js, Node.js, and DBs.
Comfortable jumping into messy code, broken APIs, and mysterious bugs.
If your project works in theory but not in reality, I help close that gap.
David Olverson
Solo dev shipping production apps with AI-assisted development. I specialize in rescuing broken Lovable/Bolt/Cursor builds and taking them to production. 10+ apps shipped including SaaS CRMs, gaming platforms, real estate tools, and Discord bots. Stack: Next.js 16, TypeScript, Tailwind CSS, FastAPI, PostgreSQL, Prisma. I use Claude Code with 50+ custom skills for rapid delivery. Average turnaround: 2-4 weeks from broken prototype to production.
Milan Surelia
Milan Surelia is a Mobile App Developer with 5+ years of experience crafting scalable, cross-platform apps at 7Span and Meticha. At 7Span, he engineers feature-rich Flutter apps with smooth performance and modern UI. As the Co-Founder of Meticha, he builds open-source tools and developer-focused products that solve real-world problems.
Expertise:
💡 Developing cross-platform apps using Flutter, Dart, and Jetpack Compose for Android, iOS, and Web.
🖋️ Sharing insights through technical writing, blogging, and open-source contributions.
🤝 Collaborating closely with designers, PMs, and developers to build seamless mobile experiences.
Notable Achievements:
🎯 Revamped the Vepaar app into Vepaar Store & CRM with a 2x performance boost and smoother UX.
🚀 Launched Compose101 — a Jetpack Compose starter kit to speed up Android development.
🌟 Open source contributions on Github & StackOverflow for Flutter & Dart
🎖️ Worked on improving app performance and user experience with smart solutions.
Milan is always happy to connect, work on new ideas, and explore the latest in technology.
Matt Butler
Software Engineer @ AWS
Antriksh Narang
5 years+ Experienced Dev (Specially in Web Development), can help in python, javascript, react, next.js and full stack web dev technologies.
Kingsley Omage
Fullstack software engineer passionate about AI Agents, blockchain, LLMs.
Caio Rodrigues
I'm a full-stack developer focused on building practical and scalable web applications. My main experience is with **React, TypeScript, and modern frontend architectures**, where I prioritize clean code, component reusability, and maintainable project structures.
I have strong experience working with **dynamic forms, state management (Redux / React Hook Form), and complex data-driven interfaces**. I enjoy solving real-world problems by turning ideas into reliable software that companies can actually use in their daily operations.
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I'm also comfortable working across the stack when needed, integrating APIs, handling business logic, and helping transform prototypes into production-ready systems.
My goal is always to deliver solutions that are **simple, efficient, and genuinely useful for the people using them.**
rayush33
JavaScript (React.js, React Native, Node.js) Developer with demonstrated industry experience of 4+ years, actively looking for opportunities to hone my skills as well as help small-scale business owners with solutions to technical problems
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Get HelpFrequently Asked Questions
How do I test for race conditions?
Use a load testing tool to send 50-100 concurrent requests that modify the same record. Check if the final state is correct. For example, if 100 requests each increment a counter by 1, the final value should be exactly 100.
What's the difference between optimistic and pessimistic locking?
Optimistic locking allows concurrent reads and detects conflicts at write time (using version numbers). Pessimistic locking prevents concurrent access with database locks. Use optimistic for read-heavy workloads, pessimistic for write-heavy ones.