Playwright developer needed for deterministic marketplace purchasing automation

I’m looking for an experienced developer to build a fast, deterministic application that monitors an online marketplace and automatically purchases listings that satisfy predefined rules. This is not an AI or LLM project. All monitoring, filtering, validation and purchasing decisions must follow explicit rules and execute consistently with minimal latency. The relevant marketplace permits automated purchasing. The project must operate within its authorised functionality, rate limits and terms of service. It does not require bypassing CAPTCHAs, queues, access controls or security protections. The marketplace name, target listings, purchasing criteria and detailed transaction flow are commercially sensitive. These will be disclosed privately during an Upwork video meeting with shortlisted candidates. The private details will not materially change the nature of the project described here. Core functionality * Run locally on a Windows computer * Maintain a persistent authenticated marketplace session * Monitor the marketplace continuously for new listings * Detect marketplace updates with minimal unnecessary requests * Evaluate listings against configurable deterministic rules * Validate multiple listing attributes before purchasing * Reject listings that fail any required condition * Initiate and complete the permitted purchase workflow automatically * Optimise the workflow for low reaction time and reliability * Prevent duplicate purchases or repeated processing * Record detections, decisions, purchases and errors in structured logs * Recover automatically from page errors, connection failures and expired sessions * Provide clear status information while the application is running * Include start, pause and emergency-stop controls * Allow important rules and settings to be changed without rewriting the application Technical preferences Playwright with Node.js is preferred, although I’m open to another deterministic architecture if the developer can explain why it would be more reliable or faster. The production decision path must not depend on: * AI or large language models * Visual interpretation of screenshots * Unpredictable agent behaviour * Manual classification of individual listings The developer should first inspect the authorised marketplace workflow and recommend the most permitted monitoring method. Where an official API or suitable authorised data source is available, it should be considered before browser browser-based monitoring. Reliability requirements The completed application should: * Run continuously for extended periods * Resume safely after application or computer restarts * Detect and report authentication failures * Avoid purchasing the same listing more than once * Preserve an audit trail explaining every purchase or rejection * Handle minor page or network delays without immediately failing * Fail safely when required information cannot be validated * Protect locally stored session and account information Deliverables * Complete source code * Working packaged application or simple local launcher * Configuration interface or clearly documented configuration file * Installation and setup instructions * Logging and error-reporting system * Testing against agreed scenarios * Live handover and demonstration * Documentation explaining how the system works * A defined bug-fix period following delivery Confidentiality and interview process I will shortlist candidates based on relevant technical experience. The marketplace identity and full commercial workflow will then be shared during an Upwork meeting. Candidates may be asked to agree to confidentiality before receiving sensitive details. All pre-contract communication will remain through Upwork, and all development work and payment will be handled through an Upwork contract. When applying, please answer the following: 1. What similar monitoring or transaction-automation systems have you personally built? 2. What experience do you have with Playwright, Puppeteer or comparable browser-automation frameworks? 3. How would you maintain and recover a persistent authenticated session? 4. How would you prevent duplicate purchases when several processes detect the same listing? 5. How would you minimise detection-to-action latency without violating rate limits? 6. How would you structure logging so every automated decision can be reviewed? 7. Would you recommend Node.js with Playwright for this project? If not, what would you use and why? 8. What information would you need during the initial technical meeting to provide a fixed quote? Please begin your proposal with the words “Deterministic automation” so I know you have read the complete specification. I’m looking for an individual developer or a small, technically focused team. Generic agency proposals will not be considered.