Our Streaming Upload Kept an Unread Copy of the Body
A relay forwarded video bytes while retaining an unread branch. The repair had to preserve early error delivery as well as bounded memory.
Reviewed by Dmytro Nasyrov on October 27, 2026.
Our admin relayed a long video upload as a stream and still ran out of memory. The downstream sink had received 292 MiB when the relay container hit its 384 MiB limit. Bytes were moving, so a progress indicator looked plausible. The process was also retaining bytes it had already forwarded.
This happened while we were adding video and image sources to a medical learning platform. The failure occurred in the transport path, before a model read anything. We reproduced it with a sink backend and synthetic data, separating the relay from document parsing and inference.
Following the branch that nobody consumed
We checked three suspects in the recorded investigation. The framework's proxy did not match the API route. The upstream fetch used a no-store policy, so its cache key was not holding the upload. The request body itself could be consumed with backpressure. None explained why resident memory grew with the transferred file.
The decisive branch belonged to the fetch implementation in the pinned Node runtime. Its request-cloning path teed the stream, leaving an original branch unread. Forwarding chunks on one branch left them retained on the other. A test that only watched the sink receive data would miss the defect.
The historical probe recorded 488 MiB RSS for a 400 MiB streamed body on one runtime, and 430 MiB for a 1 GiB zero-filled stream in the application image. Changing the relevant fetch options brought those observations to 97 MiB and 143 MiB. These are reproduction measurements from that environment, not memory limits promised for every framework or runtime release.
The first repair broke a different contract
The relay's upstream did not redirect uploads, so refusing redirects removed the problematic clone path. The investigation also tested a window option. Later review identified refusing redirects as the decisive condition in that Node implementation. Repeating both options as an unexplained universal recipe would lose that finding.
Removing the extra branch exposed cancellation. If the backend answered early with insufficient storage, fetch could cancel its input immediately. That cancellation reached the browser's request body while the relay was still trying to deliver the useful error response.
Flat memory was insufficient evidence for a correct upload.
| Observation | What it established |
|---|---|
| Sink receives bytes | The relay forwards data; retention is still unknown |
| RSS stays bounded | The unread clone is gone; response delivery is still unknown |
| Early storage refusal arrives intact | The browser can receive the backend decision |
| Body is released after the response wait | Cleanup respects the relay's response lifetime |
A stream can forward pulls while owning cancellation separately
The accepted second repair placed a pull-through stream between fetch and the counted browser body. It used a zero high-water mark and forwarded demand, while its cancellation did not cancel the counted body. The existing response-wait path retained responsibility for letting that body go. This was a narrow ownership decision, not a reason to ignore cancellation throughout an application.
In the re-review harness, the complete storage refusal arrived at 72 ms and the request was released at 4,063 ms, with flat memory. The separation mattered: the server produced its answer before the relay finished the period during which it needed the browser connection.
browser body -> counted stream -> pull-through stream -> upstream fetch
cancel stops here
response wait -------------------------------------> release browser bodyThe long file was a separate acceptance check
A later staging run recorded one long request lasting 491 seconds, with admin peak memory at 76 MiB. That result supported this repaired upload path. It did not prove that every supported video codec, every proxy or every browser handled the same file, and it was not an inference throughput benchmark.
The useful reproduction combined a memory limit, a sink that could accept a long body and an upstream that could refuse early. Using only a real parser would make a failed run ambiguous: the process might die while relaying, spooling, decoding or describing a slide. Giving those stages separate controls made the regression attributable.
One limitation remained explicit. When the backend died midway through an upload, the old catch path could stop the response wait without releasing the browser body itself. The record left that behavior for a follow-up, bounded by the connection's other lifetime controls. The successful memory repair did not close it.
What belongs in an upload regression
We would retain both assertions from this case: transferred bytes must not imply retained bytes, and canceling an upstream consumer must not destroy the response the relay is still delivering. A body-count assertion, a memory observation and an early-refusal response exercise different responsibilities. The code and measurements described here are historical implementation evidence. We have not rerun that medical product's upload suite for this article. For another runtime version, the first step is to reproduce which stream owns each branch, then check memory and error delivery under the actual transport stack.
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How long have you been in business?
Pharos Production has been in business since 2013, with over 13 years of experience in custom software development. During this time, we have delivered over 110 applications for 200+ clients across 28 industries, including FinTech, healthcare, crypto and e-commerce. We are rated 5/5 on Clutch based on 107 verified reviews (2026).
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What services do you provide?
Pharos Production provides six core service categories: AI Development (LLM applications, AI agents, machine learning and computer vision), Blockchain and Web3 (smart contracts, DeFi, tokenization on Ethereum, Solana, TON and other chains), FinTech Development (payment platforms, digital banking, KYC and AML integration), Software Development (mobile apps, web platforms, database design, UI/UX), Security and QA (code audits, penetration testing, smart contract audits, manual and automated testing) and Consulting (architecture design, MVP validation, startup consulting).
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Where is Pharos Production located?
Pharos Production is headquartered in Las Vegas, Nevada, USA (5348 Vegas Dr, Las Vegas, NV 89108), with an engineering office in Kyiv, Ukraine (44-B Eugene Konovalets Str. Suite 201, Kyiv 01133). We work with clients worldwide and provide remote collaboration across all time zones. Visit our contact page for directions and scheduling options.
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How big is your team?
Pharos Production has a team of 90+ engineers, including software developers, blockchain specialists, QA engineers, DevOps experts, UI/UX designers, project managers and solution architects. Our founder, Dr. Dmytro Nasyrov, holds a PhD in Artificial Intelligence and leads the technical direction of all projects.
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What types of customers do you serve?
We serve a wide range of clients, from startups and product companies to mid-sized enterprises and large institutions. Our clients include crypto exchanges, FinTech providers (like Pleenk), healthcare organizations, sportsbook operators (like Pro Gambling), e-commerce platforms and SaaS companies. Pharos Production has worked with 200+ clients across 28 industries since 2013, adapting engagement models to match each client's stage, whether it is MVP validation for a startup or enterprise-scale development for an established business.
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How is a custom software development company different from an agency?
A custom software development company like Pharos Production assigns one dedicated engineering team that owns your product across multiple release cycles, instead of handing it off once a contract ends. Agencies more often rotate staff between clients and optimize for fast delivery over long-term product ownership.
Pharos Production keeps the same team on your codebase through 2-week sprints, so there is no re-onboarding cost each time you request a new feature.
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How much does custom software development cost?
Custom software development costs vary based on project scope and complexity. At Pharos Production, typical project ranges are: MVP development ($10,000-$25,000), suitable for startups validating a product idea; full-fledged production ($25,000-$50,000), for established businesses scaling a proven concept; and full-cycle development ($50,000-$80,000+), for complex enterprise-grade systems. These ranges include architecture design, development, QA testing and deployment. Hourly rates range from $50 to $99 depending on role and seniority. Final pricing depends on technology stack, number of integrations and engagement model (staff augmentation, dedicated team or project outsourcing).
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How long does it take to develop a custom software application?
Development timelines depend on scope and complexity. At Pharos Production, a typical MVP takes 2-4 months, a production-ready application takes 4-8 months and a complex enterprise system can take 8-12+ months. We use an agile methodology with 2-week sprints, delivering working increments after each sprint. Every sprint includes a retrospective, progress report and planning session for the next iteration. This approach ensures transparency and allows businesses to launch faster by prioritizing high-impact features first. Get a timeline estimate for your project.
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What industries does Pharos Production serve?
Pharos Production serves 28 industries: FinTech, MiCA Compliance, Banking, Insurance, Crypto, Healthcare, Fitness, E-Commerce, Food & Restaurant, On-Demand, Manufacturing, Automotive, Energy, Oil & Gas, Supply Chain, Construction, Real Estate, Gaming, Streaming, Media, Telecom, Education, Aviation, Travel, Logistics, Marketing, Agriculture and Recommender Systems. Our deepest expertise is in FinTech, blockchain and healthcare, where we have delivered compliance-ready platforms (HIPAA, PCI DSS, GDPR) and high-load systems handling thousands of concurrent users. For the latest industry insights, read our guides on FinTech trends in 2026 and the Web3 technology stack.
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Why hire a software development company instead of building in-house?
Hiring a software development company offers faster time-to-market, lower upfront costs and access to specialized expertise without long-term employment commitments. According to Deloitte's 2024 Global Outsourcing Survey, 57% of companies outsource software development to access skills they cannot hire internally.
Factor In-house team Software development company Time to assemble 3-6 months (recruiting + onboarding) 1-2 weeks Upfront cost High (salaries, benefits, equipment) Lower (project-based pricing) Specialized expertise Limited to who you can hire locally Access to 90+ engineers across blockchain, AI, FinTech Scalability Slow (each new hire takes months) Fast (scale up or down per sprint) Long-term commitment Full-time employment contracts Flexible engagement models Risk High if key engineers leave Company ensures continuity and knowledge transfer For businesses that need blockchain, AI or high-load architecture expertise, outsourcing to a specialized firm like Pharos Production reduces risk and accelerates delivery.
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What projects does Pharos Production not take on?
Pharos Production focuses on mid-to-large custom software projects with budgets starting at $10,000. We do not take on template-based websites, WordPress theme customization or short-term contracts under one month. We also do not provide non-technical staffing (marketing, sales or design-only roles). Our strongest fit is blockchain, FinTech and healthcare projects where security, compliance and high-load architecture are critical. For smaller projects or MVPs under $10,000, we recommend exploring freelance platforms or no-code tools as a more cost-effective starting point.
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Why does Pharos Production use agile methodology?
We use agile with 2-week sprints because it reduces the risk of building features that miss the mark. Each sprint ends with a working demo, a retrospective and a plan for the next iteration.
This means clients see progress every 14 days and can adjust priorities based on real results, not assumptions. We chose this approach after years of experience showing that rigid, fixed-scope contracts lead to scope creep, missed deadlines and products that do not match market needs by launch day.
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When should you NOT hire a custom software development company?
Custom development is not the right choice in every situation. You should not hire a custom software company if: your problem is fully solved by an existing SaaS product (e.g. Shopify for e-commerce, Salesforce for CRM); your budget is under $10,000 and timeline is under 4 weeks; you need a simple landing page or marketing website (WordPress or Webflow is faster and cheaper); or you are still validating the idea and have not spoken to potential users yet.
In these cases, off-the-shelf tools or no-code platforms offer better ROI. Custom development makes sense when you need unique workflows, regulatory compliance, high-load architecture or competitive differentiation that packaged software cannot provide.
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What kind of projects has Pharos Production delivered?
Here are three anonymized examples from our recent delivery history:
FinTech startup - payment platform (MVP)
Scope: mobile app + backend API with bank-grade encryption. Team: 4 engineers, 1 QA. Timeline: 10 weeks. Budget: $38,000. Result: launched on schedule, processed $2M+ in transactions within the first quarter.Healthcare provider - patient portal (Full product)
Scope: HIPAA-aligned web platform with EHR integration, appointment scheduling and telemedicine. Team: 6 engineers, 1 DevOps, 2 QA. Timeline: 6 months. Budget: $120,000. Result: 15,000+ active patients, zero compliance violations in two annual audits.Crypto exchange - trading engine (Complex)
Scope: high-load matching engine handling 50,000+ orders per second, multi-chain wallet infrastructure on Ethereum and Solana. Team: 8 engineers, 2 QA, 1 security auditor. Timeline: 11 months. Budget: $340,000. Result: 99.97% uptime, passed three independent security audits.See more projects: NoMoreBets, Pulse, Sagas, Gambit Stream and Pleenk. For the full portfolio, visit our case studies. Learn more about the technology behind these projects in our guide to stablecoins and crypto infrastructure.
Dmytro Ihnatov is the Lead Backend Developer at Pharos Production. He documents backend architecture and research experiments from the team's work on a professional learning platform for aesthetic medicine.
