Senior Backend Engineer

Kiwi Financial Inc · Colombia

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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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