Kalendae has been operating in the Brazilian market since 2005, providing co-sourcing and consulting services, as well as application development, information security, infrastructure consulting (on-premises and cloud), and training in IT and business service management. We pursue continuous improvement of our services to ensure customer satisfaction and employee fulfillment. Requirements: We are seeking a Senior Backend Developer to work on a highly critical platform handling high transaction volumes and integrations with game providers, payment processors, KYC services, and anti-fraud solutions. You will be responsible for designing, developing, and evolving complex integrations across multiple platforms, ensuring security, high availability, low latency, and scalability. Responsibilities: * Design, develop, and maintain high-performance, well-structured RESTful APIs. * Build and maintain robust integrations with external providers (e.g., payments, KYC, anti-fraud, gaming providers, notification gateways, etc.). * Work with asynchronous events and message queues (e.g., Redis, Kafka, SQS or similar) to ensure scalability and resilience. * Ensure integration security by protecting APIs against attacks (e.g., rate limiting, authentication, authorization, input validation, etc.). * Optimize database queries and performance for relational databases (MySQL, PostgreSQL) and NoSQL systems. * Use caching (e.g., Redis and similar) to reduce latency and increase throughput. * Implement and maintain automated tests (unit, integration, and, where applicable, contract tests). * Document APIs and integration flows using Swagger / OpenAPI, Postman, or similar tools. * Collaborate with Frontend, DevOps, and Security teams on complex architectural solutions. * Help evolve architectural standards, code quality, logging, metrics, and observability practices. Mandatory Requirements: * Solid backend development experience with PHP (Laravel) and hands-on experience with at least one other modern backend language (Node.js or Java). * Strong knowledge of the Laravel ecosystem: Eloquent, Events, Jobs, Middlewares, Queues, Multi-tenant. * Proven experience integrating third-party APIs, including authentication and security mechanisms: OAuth2, JWT, API Keys, Webhooks, WebSockets. * Proficiency in databases: Relational (MySQL, PostgreSQL); Non-relational (NoSQL): Redis, MongoDB and/or DynamoDB. * Experience with caching, performance optimization, and monitoring using tools such as Sentry, Grafana, Prometheus, ELK/EFK or similar. * Strong debugging and problem investigation skills for legacy systems and complex integrations, including log analysis, distributed tracing, and production behavior analysis. * Practical knowledge of Cloud (AWS) and containerization with Docker. * Experience with Git, code reviews, and version control best practices. * Ability to work autonomously, demonstrate ownership, and communicate effectively within the team. Nice-to-have: * Prior experience in iGaming, sports betting, payment processing, or fintechs. * Certifications in AWS, Google Cloud, Azure, or Laravel. * Experience with microservices, Event Sourcing, and CQRS. * Knowledge of security and compliance standards: PCI-DSS, LGPD, GDPR, OWASP best practices. * Experience with container orchestration (Kubernetes, Helm) and resilience / disaster recovery strategies. * Experience with feature flags, A/B testing, and experimentation. Location: Nova Lima - MG, Barueri - SP, Londrina - PR, or Recife - PE. Work model: Hybrid Contract type: PJ (individual contractor) Start date: Immediate