Mirrai Careers

Backend Engineer

Kiwi Financial Inc

Colombia Remote Full-time Posted 2d ago
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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.

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