Senior Backend Engineer - AI platform

At Similarweb, we are revolutionizing the way businesses interact with the digital world by revealing to them everything that happens online. Our unique data and solutions empower thousands of customers globally, including industry giants like Google, eBay, and Adidas, to make game-changing decisions that drive their digital strategies. In 2021, we went public on the New York Stock Exchange, and we continue to reach new heights! Come work alongside Similarwebbers across the globe who are bright, curious, practical, and good people. Why is this role so important at Similarweb? AI is transforming how Similarweb operates, but scaling it requires a robust, production-grade foundation. Instead of every product and internal engineering team reinventing infrastructure, we are building a centralized, high-throughput AI Platform. As a Senior Backend Engineer (AI Platform), you will design and implement the resilient core services powering our AI ecosystem: high-concurrency agent runtimes, distributed tool and data pipelines, low-latency model gateways, and real-time evaluation and observability systems. Your internal customers are teams across the whole company, including engineers, data scientists, back office and product teams - your systems will turn AI prototypes into scalable, fault-tolerant production services deployed across Similarweb. You will not build isolated AI features; you will build the scalable platform layer that handles state management, routing, and system reliability for dozens of high-throughput AI workflows. What will you be doing? Core Systems Design: Architect and build the high-availability agent platform - focusing on distributed orchestration, state/memory persistence layer performance, event-driven execution, and a high-performance Python SDK. API & Integration Architecture: Design and operate scalable tool and connector services, including standardized Model Context Protocol (MCP) servers, gRPC/REST endpoints, and secure wrappers for Similarweb data stores, internal microservices, and external APIs. Low-Latency Model Infrastructure: Build low-latency model gateways, connection pooling, automated failover routing, semantic caching layers, and rate-limiting infrastructure. Security & Governance: Implement zero-trust security patterns at the platform layer: fine-grained access control (RBAC/ABAC), isolated data boundaries, PII detection pipelines, and high-throughput audit logging. Reliability & Performance Engineering: Optimize distributed execution to ensure strict SLA compliance, minimizing end-to-end latency and compute costs while ensuring system observability through distributed tracing and custom metrics. This is the perfect job for someone who brings: 5+ years of software engineering experience in backend development, with advanced proficiency in Python and backend system architecture. Strong system design background: Experience building asynchronous microservices, REST/gRPC APIs,…