Full-Stack Developer (Next.js + FastAPI + AI Integration) — 12-Week MVP Build

Thanks for the detailed description — the scope is clear and quite interesting.

Based on the requirements (client-side encryption, WebAuthn, AI integrations, and rate-limited external APIs), this is a fairly complex, security-sensitive system that goes beyond a typical full-stack build and requires careful architecture and implementation.

For a 12-week engagement at 30–40 hours/week, my estimate for full delivery of the described scope would be in the range of **$35K–$45K**, depending on the final depth of the security layer and integrations.

If needed, we can also break this into phases (e.g., MVP → security layer → integrations) to better align with budget and priorities.

Regarding the international background check — that’s not an issue from my side.
…
Happy to discuss scope details and adjust accordingly.

I have worked on fullstack projects, including Nodehost.ru, where the frontend was implemented in Next.js (App Router), and the backend was in Node.js (NestJS) with PostgreSQL. I was responsible for the API, database structure, and integration with external services. The most challenging part was working with third-party APIs under high load: it was necessary to control parallel requests, optimize SQL queries, and establish stable asynchronous logic between the frontend and backend. Although my primary experience is in Node.js, I am also familiar with Python/FastAPI and understand similar approaches to routing, DI, and database handling.

In terms of security and client-side data processing, I used the Web Crypto API, am familiar with AES-GCM, and approaches to key generation. The main principle is that data is not transmitted or stored in plain text, keys remain on the client, and the server only works with encrypted information.

In my daily work, I actively use AI tools such as Claude and Cursor. For example, in the past week, I used Claude for generating and refining API logic, optimizing SQL queries, debugging asynchronous issues in Node.js, and speeding up refactoring and writing boilerplate. This allows me to work faster and focus on architecture and complex tasks.

To work with external APIs with request limits (for example, 25 per day), I would implement server-side caching with TTL (Redis or PostgreSQL), deduplication of identical requests, a queue with rate limiting, and a fallback to cached data when the limit is reached. At the same time, I would log usage to optimize the caching strategy over time.

Although I do not have direct experience with fintech APIs like Plaid, I have worked with data-heavy applications and integrations where I faced challenges in ensuring data consistency under high load, handling errors from external services, idempotency of operations, and maintaining security and access control.

Show original

Translate

I worked on Poseidon (https://poseidon.codezerogroup.com) — an enterprise web platform with a Python backend, data pipelines, and analytical panels for the industrial sector.

Next.js 14 + FastAPI + Claude API is my daily stack. The scope of this offer matches 1:1 with what I do.

What I will do:
- frontend Next.js 14 (App Router, Tailwind, Radix UI)
- backend FastAPI + PostgreSQL (schema, migrations, optimization)
- AES-256-GCM encryption + Argon2, WebAuthn + TOTP
- integration of Claude/Anthropic with prompt caching and streaming
… - integration of Plaid + market data, cache + rate limit management
- deployment on Render, E2E tests, documentation + handover

Q: Background check — no problem.
Q1: Poseidon — React frontend + Python backend, the hardest part: syncing the state of calculations server↔UI, solved by WebSocket.
Q2: Web Crypto API (AES-256-GCM), Argon2 keys derived in the browser, the server only holds an encrypted blob.
Q3: Cursor + Claude daily. This week: the agent generated FastAPI endpoints + Pydantic + edge-case tests for the parser.
Q4: Redis TTL 1h, pre-fetch before expiration, 25 req/day = scheduler with exponential backoff.
Q5: Poseidon — financial pipeline, TCO calculators. Challenges: Decimal instead of float, audit trail, data retention.

--- OPTIONS ---

A) MVP Core — 9000 USD (84 days) — frontend + backend + AI API + auth, without Plaid
B) Complete implementation — 14400 USD (84 days) — full scope + Plaid + market data + deploy — best scope/price ratio
C) Extended support — 18720 USD (84 days) — like B + 3 months of support, monitoring, 2 rounds of revisions

Delivery time: 84 days. I need a repo, specifications, and a testing environment.

Portfolio:
- https://poseidon.codezerogroup.com — enterprise Python/React, data pipelines
- https://nyxvx.com — Next.js, Epic Games MegaGrant
- https://ou-uv.com — Flask/Python CMS, API integration

8 years in Python backend — from simple REST APIs to enterprise computing platforms.

Ready for a conversation this week.

P.S. Since I am new to the freelancehunt service and want to quickly gain a few initial projects for my portfolio, I am offering a 15% discount for the first 5 clients. The offer is valid until 5 orders are obtained.

Show original

Translate

Hello, tech team — github.com/Tehniki-Dev
Question 1. We built full-stack systems on Next.js + FastAPI. The most challenging part is streaming responses from AI when an error occurs after the headers have been sent. We solved this with built-in error signals directly in the stream, the client processes it through a custom hook.
Question 2. This is our usual practice in web3 projects — zero-knowledge architecture, AES-256-GCM through the Web Crypto API, Argon2 through WebAssembly for key derivation. The server never sees the plaintext. The most challenging part is key rotation without data loss within the session.
Question 3. We use Cursor + Claude daily. Last week we generated migrations and complex SQL with window functions — the development time for the analytics module was halved.
Question 4. Redis with a long TTL, stale-while-revalidate — we show the cache while a new request is processed in the background, a priority queue for active users.
Question 5. We built financial systems with atomic transactions. We solved race conditions during simultaneous debits through serializable isolation in Postgres and strict audit logs.
Background check — no problem. Write to us, and we will discuss the details.

Show original

Translate

Hello!
I noticed that my core stack is a 90% match for this role. I’d love to send my CV via DM so we can discuss how I can help.
Thank you for your time; I look forward to hearing from you!

Hello. I have been working with React/Vue/Node.js for more than 8+ years.I'm ready to cooperate.

Hello,

Background check is fine.

**Q1:** My most relevant project is airoleplay.fun - a fullstack AI SaaS I built end-to-end. The AI layer is deep: streaming responses, infinite-context workers that compress and summarize chat history to bypass token limits, per-tier state trackers, per-model prompt and settings management, token usage tracking across tiers. My primary stack is PHP/Laravel, but I've always worked across ecosystems - Python, Next.js, Vue, FastAPI and others depending on the project.

**Q2:** I'm familiar with encryption patterns - symmetric encryption, key derivation, secure storage, client-side encryption at rest.

**Q3:** Claude Code and Cursor are part of my daily workflow. I use AI for code review, generating data models, writing API specs, and debugging - it's a standard part of how I work, not an experiment.
…
**Q4:** Cache responses in PostgreSQL or Redis with a cache_key and timestamp. Cache-first logic with TTL. Request deduplication so simultaneous triggers fire only one API call. Daily budget counter - serve stale cache with a warning instead of erroring out when the limit approaches.

**Q5:** I've integrated crypto payments and LiqPay - webhook handling, transaction reconciliation, idempotency, failure recovery. The fintech mindset (retry logic from day one, append-only records, zero error tolerance) I understand well.

Hello.

I'm NodeJS developer. I have experience with NextJS. Ready to work.

Hello! My partner (designer + full-stack) and I have been specializing for over 4 years in developing architecturally complex solutions on Next.js (App Router) and FastAPI, paying special attention to data security and the integration of AI models. We are implementing a platform for you with client-side encryption (AES-256-GCM), setting up streaming response generation from Claude, and ensuring technically flawless synchronization with financial APIs (Plaid). Our experience in development is 4 years; take a look at our work in terms of performance and security: hyperfi.tech, espressolab.com.ua, hudi.com.ua. We professionally work with WebAuthn and complex PostgreSQL schemas, guaranteeing compliance with the highest security standards. Our 4 years of experience is confirmed by successful cases of developing fintech services and systems with intensive use.

We value the opportunity to provide detailed answers to your questions and confirm our full readiness to undergo an International Background Check before starting cooperation. Our team has extensive experience in developing high-load systems on the Next.js and FastAPI stack, particularly in asset monitoring projects, where a critical challenge was synchronizing states between long computations on the backend and the client interface; we successfully solved this task by implementing a WebSocket-based architecture for instant statuses and Redis for efficient caching of intermediate data. In terms of security, we have practical experience in implementing Zero-Knowledge architecture with client-side encryption: using the Web Crypto API (AES-256-GCM) and Argon2 via WebAssembly, we ensured a level of confidentiality where access keys never leave the user's browser. AI tools, including Cursor and GitHub Copilot, are an integral part of our workflow, allowing us to significantly speed up the writing of complex SQL queries with window functions and automate the generation of database migrations without losing quality. To work under strict limits of external APIs, we implement a multi-layered strategy: aggressive caching in Redis, a Stale-While-Revalidate mechanism for uninterrupted data access, and intelligent queue management with prioritization of requests for active sessions. It is also worth noting our expertise in financial operations gained during the development of banking platforms, where we ensured complete atomicity of transactions and eliminated race condition risks by using the SERIALIZABLE isolation level in PostgreSQL and implementing a strict audit system for each log.

Show original

Translate

Hello! My partner (designer + full-stack) and I have been specializing for over 4 years in developing architecturally complex solutions on Next.js (App Router) and FastAPI, paying special attention to data security and AI model integration. We are implementing a platform for you with client-side encryption (AES-256-GCM), setting up streaming response generation from Claude, and ensuring technically flawless synchronization with financial APIs (Plaid). Our experience in development is 4 years; take a look at our work in terms of performance and security: hyperfi.tech, espressolab.com.ua, hudi.com.ua. We work professionally with WebAuthn and complex PostgreSQL schemas, guaranteeing compliance with the highest security standards. Our 4 years of experience is confirmed by successful cases of developing fintech services and data-intensive systems.
Answers to your questions:
International Background Check: This is not a problem. We are ready to undergo a check before starting.
Q1: Project Next.js + FastAPI. Developed an asset monitoring system. The most challenging point was synchronizing the frontend state with long computations on the backend. We solved it through WebSocket for statuses and Redis for caching intermediate results.
Q2: Client-side encryption. Yes, we implemented a "Zero-Knowledge" architecture. We used the Web Crypto API for AES-256-GCM (browser support) and Argon2 (via WebAssembly) for deriving keys from the user's password. The keys never left the client side.
Q3: Use of AI. AI is part of our DNA. A specific example: last week we used Cursor (Composer) for rapid generation of database migrations and writing complex SQL queries with window functions, which halved the development time of the analytics module.
Q4: API caching (25 requests/day). 1. Aggressive Caching: Storing results in Redis with a long TTL. 2. Stale-While-Revalidate: Showing cached data while a new request is processed in the background (if the limit allows). 3. Queue Management: A queue of requests with prioritization (priority for active users).
Q5: Financial data. We worked on a children's banking system. The main challenge was the atomicity of transactions and preventing "race conditions" during simultaneous fund withdrawals. We solved it through SERIALIZABLE transaction isolation in PostgreSQL and strict log auditing.

Show original

Translate

Hello, I did a very similar project, I also deployed it on render with the integration of artificial intelligence, write to me, I will send the link.

Show original

Translate

Good day.
I am interested in your project, as it is exactly the type of full-stack tasks where it is important to simultaneously maintain the quality of the frontend, the reliability of the backend, data security, and a neat integration with external APIs. I work with Python/FastAPI, PostgreSQL, API integrations, server logic, as well as with modern web stack at the level of full business logic, roles, security, forms, dashboards, integrations, and deployment.

Show original

Translate

Hello,

I’m interested in this project because it matches my experience with Next.js, FastAPI, PostgreSQL, API integrations, and AI-assisted development workflows. I’m comfortable working across the full stack and building secure, data-driven applications with clear architecture and reliable implementation.

Passing an international background check is not an issue.

**Q1:** I’ve worked on projects where I handled both the frontend and backend. The most challenging part was usually coordinating async flows between the UI and backend processing while keeping the user experience smooth and error handling clear.

**Q2:** I’m familiar with client-side encryption approaches using the Web Crypto API, with AES-256-GCM for encryption and Argon2 for key derivation. My focus is on encrypting sensitive data on the client, managing IVs and salts properly, and keeping secrets out of logs and backend exposure.
…
**Q3:** I use AI tools daily for scaffolding, debugging, refactoring, and speeding up repetitive tasks. Recently, I used AI to help restructure backend integration logic, then manually reviewed and refined the result to ensure it fit the architecture and edge cases.

**Q4:** For a rate-limited API, I would use a cache-first approach with TTL-based caching, request deduplication, quota tracking, and graceful fallback to cached data when limits are reached. I’d centralize this logic in a service layer so usage stays controlled and predictable.

**Q5:** I’ve worked on data-sensitive systems where accuracy, consistency, and trust were critical. In finance-related work, the biggest challenges are usually secure handling of data, normalization across sources, auditability, and making sure users can rely on the outputs.

Best regards
Nikola

Hello! 🚀

I have experience in developing full-stack SaaS solutions: Next.js + FastAPI + PostgreSQL, integrating AI (Claude/OpenAI), working with APIs, and building scalable architecture. I have worked with sensitive data, implemented client-side encryption (AES-GCM), caching, and query optimization.

The stack I use:

Backend: Python (FastAPI), PostgreSQL, Redis
Integrations: *AI API (Claude/OpenAI), third-party APIs, caching, rate limit
Frontend: Next.js, TypeScript, Tailwind
… Infrastructure: Docker, CI/CD, secure architecture

Q1:
I developed a SaaS application (dashboard + analytics): Next.js + FastAPI.
The most challenging part was integrating streaming AI responses into the UI (partial updates + state synchronization). This was solved through WebSocket + caching.

Q2:
Yes. I used Web Crypto API (AES-GCM), keys through PBKDF2/Argon2. Data is encrypted on the client side, and the server only stores the encrypted payload.

Q3:
I use Claude/GPT/Cursor: code generation, refactoring, tests.
Example: I optimized an SQL query and rewrote the processing for batch.

Q4:
Cache (Redis/PostgreSQL) + TTL, rate limit, request queue, deduplication, fallback to cache under limits.

Q5:
I have worked with financial data (dashboards, transactions).
Challenges: accuracy of calculations, consistency, security, handling edge cases (rollback, partial operations).

I am ready to discuss the details in private!

Best regards,
Andriy

Show original

Translate

Hello! After reviewing your project, I am ready to start working on it. I can offer optimal solutions to achieve the best result.

Show original

Translate

Good day.

I have experience in the full development cycle: from frontend on Next.js to backend on FastAPI with PostgreSQL, including integrations with AI APIs and third-party services.

I have worked with data-heavy systems where performance, data structure, and stability of integrations are important. I have experience with caching, asynchronous processing, streaming responses, and query optimization.

I have implemented secure solutions, including working with tokens, data encryption, and authentication. I have also worked with integrations of financial and third-party APIs.

I use AI tools daily (Claude Code, Copilot) for analysis, refactoring, and speeding up development.
…
I am ready to work in your format (30–40 hours/week), participate in technical decision-making, and move through the PR workflow.

Background check is not a problem.

Q1:
I worked on a project with FastAPI + frontend, where the complexity was in synchronizing the state between the backend and the client during asynchronous AI requests and streaming responses. I solved this through a clear API contract and state control on the client.

Q2:
I used a client-side processing approach for sensitive data before sending it to the server, using standard cryptographic libraries of the browser (Web Crypto API). The main focus is not to store open data on the server.

Q3:
I use AI for code generation and verification, identifying bottlenecks, and rapid prototyping. For example, recently I optimized part of the API and data processing structure through Claude Code.

Q4:
I would implement caching (e.g., Redis) + rate limit control on the backend. Cache responses and minimize repeated requests, add a queue and fallback logic.

Q5:
I have worked with financial data in the context of API integrations and transaction processing. The main challenges are accuracy, consistency, and handling edge-case scenarios.

Show original

Translate