Senior Backend Engineer

Job description

**Sr. Backend Engineer** We are looking for a Senior Backend Engineer with strong experience designing, building, and evolving scalable, reliable, and secure backend systems. This is a hands-on engineering role for someone who goes beyond feature implementation. We are looking for an engineer with strong technical judgment who can understand complex systems end-to-end, contribute to architectural decisions, identify and address technical debt, and continuously improve the quality and maintainability of our platform. AI is becoming a core part of how we build software. We expect engineers to effectively use modern AI-assisted development tools while maintaining strong ownership and engineering judgment over the code and systems they deliver. **Responsibilities** - Design, build, and evolve scalable backend services and APIs, primarily using Node.js, TypeScript, and Express.js. - Own technical solutions end-to-end, from design and implementation through deployment, observability, and production support. - Contribute to the evolution of our backend architecture and participate actively in architectural and technical design decisions. - Identify, prioritize, and address technical debt, balancing long-term maintainability with product delivery. - Apply solid software design principles and patterns, choosing appropriate solutions based on context and trade-offs rather than applying patterns by default. - Design clear application boundaries and separation of concerns across services, business logic, and persistence layers. - Design and optimize PostgreSQL schemas, queries, indexes, migrations, and transactional workflows. - Build reliable financial workflows with appropriate strategies for idempotency, concurrency, consistency, retries, failure handling, and reconciliation. - Design and maintain REST APIs and integrations with internal systems and external providers. - Design asynchronous and event-driven workflows when appropriate. - Build systems with strong principles around reliability, scalability, resilience, security, and performance. - Work with AWS infrastructure and cloud services as part of developing and operating production systems. - Improve production visibility through structured logging, metrics, tracing, monitoring, and alerting. - Investigate complex production incidents, perform root-cause analysis, and implement sustainable solutions rather than temporary fixes. - Maintain high engineering quality through automated testing, code reviews, documentation, and continuous refactoring. - Use AI-assisted engineering tools to improve development speed, testing, debugging, code review, and engineering productivity while maintaining human ownership of technical decisions. - Challenge existing technical decisions constructively and help continuously improve our engineering standards. - Share knowledge and contribute to strengthening the technical capabilities of the engineering team. - Collaborate closely with Product, QA, Data, Platform, and other engineers to translate business requirements into robust technical solutions. **Requirements** - 8+ years of professional backend engineering experience, with significant experience building and operating production systems. - Strong hands-on experience with Node.js and TypeScript in production environments. - Experience with Express.js or comparable backend frameworks. - Experience with Python and familiarity with backend frameworks such as FastAPI, Django, or similar is highly valued. - Strong knowledge of software architecture, design principles, and design patterns, including their trade-offs and appropriate use cases. - Strong understanding of relational databases and PostgreSQL, including data modeling, transactions, indexing, query optimization, migrations, and performance. - Experience working with ORMs and persistence patterns, understanding both their benefits and limitations. - Strong understanding of API design, authentication, authorization, versioning, security, and third-party integrations. - Experience designing systems for failure scenarios, including retries, duplicate events, partial failures, race conditions, and external-service degradation. - Solid understanding of distributed systems and asynchronous processing. - Experience with automated testing at different levels, including unit, integration, and end-to-end testing. - Production experience with AWS or comparable cloud infrastructure. - Experience with CI/CD, containers, and modern software delivery practices. - Strong understanding of observability and production troubleshooting. - Ability to analyze architectural alternatives, identify trade-offs, and clearly explain technical decisions. - Strong ownership, problem-solving, and communication skills. - Ability to work autonomously on complex technical problems while collaborating effectively with the broader team. **Nice to have** - Experience in fintech, payments, lending, banking, or other highly transactional environments. - Experience building systems where financial correctness and data integrity are critical. - Experience with event-driven architectures, queues, messaging systems, and asynchronous processing. - Experience with AWS services such as Lambda, ECS/EKS, SQS, SNS, EventBridge, RDS, S3, and CloudWatch. - Experience with Infrastructure as Code, such as Terraform or CloudFormation. - Experience with high-volume transactional systems and distributed architectures. - Experience implementing idempotency, outbox patterns, concurrency control, reconciliation processes, and fault-tolerant workflows. - Experience with observability platforms such as Datadog, Sentry, or similar tools. - Familiarity with DDD, Clean Architecture, Hexagonal Architecture, or similar architectural approaches — with the ability to understand when they are useful and when they add unnecessary complexity. - Experience using modern AI coding assistants, agents, and AI-native development workflows. - Familiarity with LLMs, tool calling, MCP, agentic workflows, or AI integrations is a plus, but AI specialization is not required. **What we offer** - The opportunity to work on critical financial products with direct impact on customers and business growth. - High technical ownership and the opportunity to influence how our backend platform evolves. - Meaningful architecture, scalability, reliability, and technical-debt challenges. - An engineering environment where AI is becoming a core part of how we build software. - A collaborative multidisciplinary team across Engineering, Product, Design, QA, Data, and Platform. - 100% remote — Argentina or Colombia. [**Apply now**](https://www.kiwicredito.com/en-us/careers?ashby_jid=15b0e285-d1d8-4fb1-a95e-fe140c15535b&utm_source=Linkedin)