MangoDesk — Founding Engineer, SWE

Type: Full-time | On-site | San Francisco, CA Compensation: $150,000–$200,000 + 0.5%–2% equity Hiring count: 2 Visa sponsorship: Yes — O-1, OPT Reports to: CEO

MangoDesk is a YC-backed startup bridging the gap between AI and the $5 trillion knowledge work economy by building data infrastructure and environments — including reinforcement learning environments that frontier AI labs use to train and evaluate their models. Its software lets AI teams create custom evaluation datasets and annotation pipelines by describing their needs in plain English, automating the entire workflow: interface generation, instructions, QA, and annotator management. The founding team brings experience from Scale AI, Uber, and a previously founded successful AI company, and recently closed an oversubscribed $3M seed round from top-tier VCs.

Founded: 2025 | Team size: 1–10 | Total funding: $3M seed (oversubscribed) Industry: AI Tools Website: mangodesk.com Office: San Francisco, CA

• Founding-level ownership: Among the first engineering hires on a lean team, reporting directly to the CEO, owning large technical scopes end-to-end.
• Frontier-adjacent work: RL environments are a key bottleneck to AI model improvement; this work feeds directly into how frontier labs train and evaluate their models.
• Momentum and backing: YC-backed with an oversubscribed seed from top-tier VCs, and a founding team out of Scale AI, Uber, and a prior successful AI company.

• Not provided in source. An intake video is present on the Contrario role page, but no transcript or written intake summary was included in the captured HTML.

Founding Engineer on a lean team reporting directly to the CEO, owning large scopes of technical pipelines end-to-end — taking ambiguous requirements from research through execution and balancing speed against reliability as the team scales.

• →Own large scopes of technical pipelines end-to-end
• →Build production-grade backend and full-stack systems
• →Set technical direction alongside the CEO
• →Make scalability and system-design decisions as the product and team grow
• →Ramp into additional scope, including new languages and tools, as needed

Tech stack: Not specified in source.

• Strong technical and computer science fundamentals
• Experience building production-grade backend or full-stack systems
• Deep understanding of scalability challenges and strong system design skills
• Ability to take ambiguous requirements, conduct research, analyze tradeoffs, and own project execution end-to-end, balancing speed and reliability
• Strong communication skills and a bias toward ownership

• Prior experience at startups or high-growth companies
• Experience with applied AI or AI research, specifically in post-training
• Background at an RL environment company or applied AI lab

• Highly dependent on rigid structures and constraints
• Resistant to change or working outside established methods
• Primarily focused on user-facing work rather than backend systems

• Salary — $150,000–$200,000
• Equity — 0.5%–2%
• On-site policy — On-site, San Francisco (in-person per outreach template)
• Visa sponsorship — O-1, OPT
• Employment type — Full-time
• Location — San Francisco, CA

• None provided in source.

Stage 1 — Pending Approval — Candidate submitted, awaiting approval. Stage 2 — Initial Screen Stage 3 — First Round Stage 4 — Second Round Stage 5 — Offer Stage 6 — Candidate Hired — Candidate accepts and starts.