Senior Python Backend Engineer / Infrastructure Architect

# Senior Python Backend Engineer / Infrastructure Architect ## Scalable Large-File Processing Platform ### About GridLine GridLine is a construction technology platform being built to dramatically simplify how contractors manage project plans, specifications, takeoffs, field documentation, and project information. The application frontend and core workflows are being developed in Base44. We are looking for an experienced backend engineer to design, improve, and implement the server-side infrastructure required to support large-scale document uploads and processing. This is not a frontend, website-design, or general CRUD-development role. The primary focus is scalable backend infrastructure, distributed processing, large-file handling, reliability, and system architecture. ### Initial Project Our immediate priority is improving the architecture of GridLine’s plan ingestion system. The platform must eventually support approximately 100 or more projects uploading and processing large construction plan sets simultaneously. Individual plan sets may contain: * 500–1,000+ PDF pages * Files exceeding 1–3 GB * High-resolution architectural and engineering drawings * Large numbers of generated images, metadata records, tiles, and processing jobs The current system uses Python, FastAPI, Celery, Redis, PostgreSQL, Docker, Railway, and AWS S3-compatible object storage. The selected engineer will begin by reviewing the existing system, identifying bottlenecks and technical risks, and recommending a practical architecture that can scale without unnecessary complexity or excessive infrastructure costs. ### Responsibilities * Review the current backend architecture and codebase * Evaluate the existing upload, storage, processing, and callback workflows * Design a scalable architecture for concurrent large-file uploads * Improve S3 multipart upload handling * Design resilient asynchronous job-processing workflows * Configure and optimize Celery workers, queues, routing, retries, and task priorities * Improve Redis and PostgreSQL usage * Implement horizontal worker scaling and concurrency controls * Prevent individual large jobs from overwhelming the system * Improve failure recovery, resumability, idempotency, and retry behavior * Add structured logging, monitoring, health checks, and useful operational metrics * Improve API security, authentication, rate limiting, and validation * Identify infrastructure bottlenecks before they affect production users * Document the architecture and provide clear deployment and maintenance instructions * Coordinate with the founder and work within the existing Base44 application architecture ### Current Technology Stack Experience with most of the following is required: * Python * FastAPI * Celery * Redis * PostgreSQL * Docker * AWS S3 or S3-compatible object storage * Multipart uploads * REST APIs * Background workers * Linux-based cloud deployments * Asynchronous and distributed processing The current backend is deployed through Railway, although we are open to practical recommendations involving AWS or another infrastructure provider when justified. ### Required Experience The ideal candidate has: * At least five years of professional backend engineering experience * Strong production experience with Python * Strong experience with FastAPI or comparable Python API frameworks * Production experience using Celery and Redis * Experience designing distributed worker systems * Experience processing large files or large volumes of files * Experience with S3 multipart uploads and object-storage architecture * Strong PostgreSQL experience * Experience designing systems for concurrency, fault tolerance, and horizontal scaling * Experience containerizing and deploying services with Docker * Strong understanding of retries, idempotency, task queues, timeouts, dead-letter handling, and failure recovery * Experience diagnosing performance and scalability bottlenecks * Ability to explain architectural decisions clearly to a technical founder ### Highly Relevant Backgrounds Candidates with experience in any of the following will receive additional consideration: * Document-processing platforms * PDF ingestion or rendering * OCR pipelines * CAD, BIM, or construction technology * GIS or map-tile processing * Medical imaging * Video transcoding * Cloud-storage platforms * Image-processing pipelines * Large media-upload systems * Data-processing or ETL platforms * AI document-ingestion pipelines Direct construction-industry experience is helpful but not required. ### Not the Focus of This Role This is not primarily a frontend role. You will not be hired to spend most of your time working on: * React interfaces * CSS * Landing pages * WordPress * Shopify * UI animations * Marketing websites * Basic administrative dashboards A candidate who describes themselves primarily as a frontend developer or general website developer is unlikely to be a good fit. ### Initial Engagement We expect to begin with a paid architecture and system-review engagement. The first phase will likely include: * Reviewing the existing repository and deployment environment * Mapping the current upload and processing workflow * Identifying failure points, bottlenecks, and security risks * Evaluating the system’s ability to support high concurrent upload volume * Recommending an implementation roadmap * Producing a concise backend architecture document * Implementing one or more high-priority improvements The initial engagement is expected to require approximately 20–40 hours. A successful initial project may develop into an ongoing fractional backend architect or senior engineering role requiring approximately 5–15 hours per week. ### Budget We are seeking a highly capable and cost-effective engineer. Expected hourly range: **$40–$80 USD per hour** Higher rates may be considered for candidates with exceptional and directly relevant large-file, distributed-systems, or infrastructure experience. Please do not apply if your rate is based primarily on frontend or full-service agency work. ### Application Instructions To be considered, begin your proposal with the phrase: **GRIDLINE BACKEND** Then answer the following questions: 1. Describe a production system you built that processed large files or a high volume of background jobs. 2. What was the largest file size, job volume, or concurrent workload that system handled? 3. Describe your experience with FastAPI, Celery, Redis, PostgreSQL, Docker, and S3 multipart uploads. 4. How would you prevent 100 simultaneous multi-gigabyte plan uploads from overwhelming an API or worker system? 5. How do you design Celery jobs so they are safe to retry and do not create duplicated data or processing? 6. What monitoring, logging, and alerting would you implement for a large-file ingestion platform? 7. Have you built systems involving PDFs, OCR, image processing, video processing, GIS, CAD, BIM, or document ingestion? Please describe the most relevant example. 8. Are you applying as an individual engineer or through an agency? 9. What is your hourly rate and weekly availability? 10. Include a link to your GitHub profile, technical portfolio, or relevant code samples when available. ### Important Generic proposals will not be considered. We are specifically looking for someone who can demonstrate real production experience with distributed systems, asynchronous processing, large-file workflows, and backend infrastructure. The right person will help build a reliable technical foundation for a construction software platform intended to scale into a major commercial product.