Founding Principal Backend Engineer

Description

Job Summary: We are seeking a backend architect to build the foundation of a sensitive, multi-tenant, and auditable platform—designed for AI-assisted workflows with traceability and permissions. Key Highlights: 1. Build the nervous system of a Deep Tech platform powered by AI. 2. Define architecture, code, and technical culture in a startup. 3. Work in an environment that values responsibility and quality. Imagine the moment when the platform stops serving ten internal users and begins handling real production load—multi\-tenant, concentrated in critical time windows. Imagine an asynchronous job failing halfway through, with no one knowing the final state of the operation. Imagine an auditor requesting traceability for a decision made six months ago—and the only possible answer being the audit logs that were—or were not—designed in the first lines of the backend. This role exists because those three scenarios are not hypothetical: they mark the moment a platform transitions from demo to product, and the difference between what scales and what must be rebuilt is decided before any of them occur. We seek someone capable of building the foundation of a sensitive, multi\-tenant, and auditable product—ready to operate AI-assisted workflows with traceability, permissions, and evidence. If those three scenarios feel familiar to you—and you have opinions on how to design for them—keep reading. https://jobs.ashbyhq.com/naiian/dae21143\-7e05\-4d56\-9126\-75859542085 **About Naiian** ---------------- Naiian is a European Deep Tech startup with a team in Madrid, well\-funded, and founded by individuals with proven track records in product, applied AI, and engineering in mission-critical environments. We build for customers operating in contexts of high operational and decisional demand—where auditability, integration with verifiable data sources, and human approval mechanisms for sensitive tasks are not features—they are foundational. We are in the founding phase. The people who join now will define the architecture, code, and technical culture the company will inherit for years to come. **The Role and Why It Exists** ----------------------------- You will build the platform’s nervous system: APIs, tenancy, authentication, RBAC, asynchronous jobs, uploads, storage logic, audit logs, service-to-service contracts, and the foundation of the AI control plane. The reason this role exists is concrete: when usage increases, when load concentrates in critical time windows, or when AI-assisted workflows begin operating with traceability, permissions, costs, and evidence—the platform must not descend into chaos. The layer you build will determine whether it does—or doesn’t. You will also deliver the first version of the AI control plane: the layer that registers, governs, and orchestrates how models, workflows, RAG, outputs, costs, latencies, and permissions are used. You don’t need to be an ML expert—but you must understand that model calls, AI jobs, events, and evidence cannot remain scattered or untraceable. **What You’ll Build in the First 6 Months** -------------------------------------------------- * V1 of the control plane: tenant isolation, workspaces, permissions, RBAC, and genuine logical isolation—not decorative. * Critical platform APIs—versioning, error handling, pagination, streaming, and progressive states where applicable. * The asynchronous jobs layer: retries, idempotency, cancellation, prioritization, and backpressure. Built to handle real load—not demos. * Audit logs and traceability from the first commit—not as a later patch. * Internal service contracts enabling AI workflows, RAG, agents, and model routing to operate with observability, clear boundaries, and ownership. * Usage metrics, per-tenant limits, cost tracking, and rate limiting—the operational foundation for governing the platform. * Build-vs-buy decisions alongside the founding team, and technical mentoring on backend standards as the team grows. **How We Work** --------------------- We work in person in Madrid. This is a deliberate decision: during the founding phase, the speed of iteration and quality of technical decisions made around a shared whiteboard are difficult to replicate remotely. We operate with minimal process and maximum responsibility. Whoever designs an API also maintains it in production. Whoever builds an asynchronous job also debugs it when it fails. We do not delegate observability, errors, or production “to DevOps”—they are part of engineering work. Quality is judged by reality: Does this hold up? Is it auditable? Can it be operated? Would another senior engineer understand it six months from now? If the answer to any is “no,” go back to the whiteboard. **What We’re Looking For** ------------------ More than a rigid profile, we seek demonstrable competencies: * Proven experience building and scaling SaaS backends in production—from 0 to 1 or 1 to n. Sensitive products, multi\-tenant systems, or those with high operational criticality. * Hands-on experience with real permissions, workspaces, tenants, and logical isolation—not just blog-post theory. * Solid asynchronous job design: retries, idempotency, backpressure, traceability. Having lived the edge cases is a plus. * Strong judgment in data modeling, API versioning, and inter-service contracts. * Ability to design audit logs and traceability for products where evidence matters. * Understanding of how to register and govern model calls, costs, latencies, and outputs—even without ML specialization. * Strong backend skills in Python and/or Go; advanced Postgres; real-world experience with observability and production debugging. * High-level English and operational Spanish—or genuine ability to work onsite in Madrid within a bilingual team. **Bonus Points If** ------------------ * You’ve worked with AI gateways, model routing, RAG pipelines, or LLM application backends. * You have experience with OpenTelemetry, Temporal, Redis/BullMQ, SQS, Kafka/NATS, pgvector, or equivalent tools. What matters isn’t having used each exact tool—but having built equivalent systems in production. * You come from fintech, healthtech, legaltech, cybersecurity, data platforms, B2B SaaS enterprise, or products handling sensitive data. * You have experience in regulated environments or with compliance and audit requirements. **What Likely Won’t Fit** ---------------------------------- To save mutual time, this role is likely not the best fit if: * You haven’t written code in some time, and your role has shifted toward architecture without shipping. * Your experience centers on CRUD applications, internal dashboards, or simple APIs—without tenancy, auditing, or real concurrency requirements. * You default to microservices before understanding the problem. * You’re a machine learning engineer considering this role as a pivot into applied ML—we seek real backend engineering. **Compensation** ---------------- **Salary:** €85,000 – €95,000 gross annually, based on demonstrated experience and validated seniority level. **Equity:** Founding equity package aligned with the founding nature of the role and the company’s stage. **Employment Type:** Full\-time, permanent, 100% onsite in Madrid. **Data Protection** ----------------------- Personal data you share with us during the process (CV, contact details, professional information, communications, and interview-provided information) will be processed by Naiian solely to manage your application for this position and—should you give explicit consent—to consider you for future compatible roles. The legal basis for processing is the implementation of pre-contractual measures at your request (Art. 6.1.b GDPR) and, where applicable, your consent (Art. 6.1.a GDPR). Your data will be retained for as long as necessary to manage your application and, unless you exercise your right to erasure, for up to one year if you authorize retention for future processes. We do not carry out automated decision-making with significant legal effects. You may exercise your rights of access, rectification, erasure, objection, restriction, and data portability—and withdraw consent—at any time by writing to the contact address shown in the application form. You have the right to lodge a complaint with the Spanish Data Protection Agency (www.aepd.es). *— Naiian Recruiting Team* Compensation Range: €85K \- €95K