Senior Backend Engineer - Typescript

Salla is looking for a Senior Backend Engineer to join our AI team. This role focuses on building the integration and infrastructure layer that connects our AI capabilities to production systems. You will be responsible for enabling AI features to operate reliably, securely, and at scale across the Salla ecosystem. Alongside this, you'll contribute to our integrity systems by owning the rule engine and business logic that turn risk signals into auditable enforcement decisions.

This role is backend-first, with a strong emphasis on TypeScript, Node.js, SDK ownership, and system integrations, while also collaborating closely with product and frontend teams to make AI capabilities easily consumable across Salla's products.

Key Responsibilities

• Design, implement, and maintain AI-focused SDKs that enable seamless communication between AI services and application layers
• Build backend services and integrations that make AI capabilities consumable across Salla's products and teams
• Develop and maintain API integrations and Model Context Protocol (MCP) servers that allow AI agents to interact with internal systems, external tools, and databases
• Design and own a versioned rule/policy engine and the supporting business logic for Salla's integrity systems — translating risk signals and model scores into auditable decisions (state → policy → action), with enforcement/actuation owned by the product team
• Model the decision records, state transitions, and audit trails that keep integrity outcomes explainable and reversible (appeals, overrides)
• Partner with the integrity/ML lead to consume risk-scoring outputs, and with product teams to define the enforcement-action contracts the engine emits against
• Ensure type-safe, scalable, and high-performance TypeScript code, following backend best practices
• Collaborate closely with frontend engineers to define AI data contracts, schemas, and interfaces
• Collaborate with frontend teams on integration contracts for AI-powered features when needed
• Optimize AI-related data flows, including streaming responses and real-time interactions
• Mentor mid- and junior-level engineers and uphold strong engineering and testing standards across AI and integrity services
• Participate in architecture discussions, code reviews, and technical decision-making

• 4+ years of backend development experience, with a strong focus on TypeScript and Node.js

• Proven experience designing and maintaining RESTful APIs and third-party integrations
• Solid understanding of relational databases (PostgreSQL or MySQL), including query optimization
• Strong knowledge of software design principles (SOLID, clean architecture, design patterns)
• Experience working with Git in structured team workflows (e.g., Git Flow, PR-based development)
• Hands-on experience with unit testing and integration testing
• Good understanding of how frontend applications consume backend services, including modern JavaScript (ES6+)

Nice to have:

• Familiarity with AI systems, including Agentic AI, LLM orchestration, or streaming AI responses
• Experience building or integrating AI-powered features into production applications
• Experience designing rules engines, policy-as-code, state machines, or complex stateful business logic (bonus: OPA/Rego or versioned decisioning)
• Strong domain and data modeling for correctness- and audit-critical systems
• Hands-on experience with modern frontend frameworks (React, Vue, or similar)
• Exposure to cloud and DevOps tooling such as Docker, Kubernetes, AWS, or CI/CD pipelines
• Experience working in cross-functional product teams involving AI, backend, and frontend engineers
• Bonus: trust & safety, fraud, risk, or marketplace integrity exposure