Senior Back-End Engineer (Must: Kotlin & Spring Boot)

Santex; United States; Remote; USD 96,000 - 165,000; Part time

Job summary

Santex is hiring a senior Kotlin/Spring Boot contractor to own the execution backbone of a no-code workflow platform. The Orchestrator runtime handles workflow execution, persistence with Temporal, and integration across HTTP, agent, LLM, and human-review nodes.

This role sits in the runtime layer that other components depend on. The candidate will design robust Kotlin/Spring Boot services, implement Temporal workflows, and ensure durable, recoverable executions within a multi-module, API-first

Qualifications

• Strong production Kotlin backend experience.
• Strong Spring Boot experience in distributed systems or platform services.
• Hands-on Temporal experience in production.
• Strong understanding of workflow durability, retries, idempotency, and recovery design.
• Experience with multi-module Gradle codebases and contract-first API design.
• Experience with JPA/Hibernate and PostgreSQL.
• Experience with Docker Compose/Test containers integration testing.
• Comfort debugging multi-service systems with mixed Kotlin and Python components.
• Experience with observability tools like micrometer
• Experience with contract first development
• Advanced English is required for this position.

Responsibilities

• Design and harden the Kotlin/Spring Boot runtime that executes workflow graphs reliably in production.
• Implement and improve Temporal.io workflows, activities, signals, queries, retries, and recovery paths.
• Strengthen contract-first APIs and shared contracts.
• Own failure-mode thinking across distributed execution retries, idempotency, partial failure, replay safety, pause/resume, and graceful degradation.
• Work across node types, including HTTP, agentic tool-calling, LLM, and human-in-the-loop review nodes.
• Improve integration coverage using Test containers and layered Docker Compose profiles.
• Collaborate closely with Composer and AI/KB teams on execution semantics and runtime behavior.
• Write clear operational documentation and runbooks for a reliability-critical service.

Skills

Kotlin backend

Spring Boot

Temporal

Distributed systems

PostgreSQL

Docker Compose

Micrometer

API design

English

Tools

Gradle

JPA/Hibernate

Docker

Test containers

Python

OAuth2/JWT

Job description

Santex is a global Certified B technology company as well as one of North America’s fastest-growing companies, according to the Inc. 5000. It’s present in 18 countries and over 100 cities, and headquartered in Argentina with offices in the United States, Mexico, and Peru.

Its two service lines — AI Tech Consulting and AI-Optimized Engineering — help organizations comprehensively adopt technology, expand their capabilities, and improve business outcomes at scale.

The same approach defines its culture: Santex has 80.4% employee engagement (global average: 21%), 8% annual turnover (tech sector: 20–25%), 9,369 training hours invested in 2025 — more than double the global average —, and a 26.5% year-over-year reduction in carbon footprint, achieving carbon neutrality through offsetting.

Santex. A company with purpose and judgment. Yes, it’s possible.

We are an Equal Opportunity Employer and are committed to fostering an inclusive and diverse workplace. We do not discriminate on the basis of race, color, religion, sex, gender identity or expression, sexual orientation, national origin, age, disability, veteran status, genetic information, or any other characteristic protected by applicable law. All qualified applicants will receive consideration for employment without regard to any of these factors. We strongly encourage candidates from all backgrounds to apply.

We’re hiring a senior Kotlin/Spring Boot contractor to help own the execution backbone of a no-code workflow platform. This is not a simple CRUD service. The Orchestrator runtime is a multi-module system that receives workflow execution requests, persists durable state with Temporal, coordinates graph execution, integrates HTTP, agent, LLM, and human-review nodes, and safely executes increasingly AI-generated workflow graphs. You’ll join the squad responsible for the runtime layer that everything else depends on.

Responsibilities

• Design and harden the Kotlin/Spring Boot runtime that executes workflow graphs reliably inproduction.
• Implement and improve Temporal.io workflows, activities, signals, queries, retries, and recovery paths.
• Strengthen contract-first APIs and shared contracts.
• Own failure-mode thinking across distributed execution retries, idempotency, partial failure, replay safety, pause/resume, and graceful degradation.
• Work across node types, including HTTP, agentic tool-calling, LLM, and human-in-the-loop review nodes.
• Improve integration coverage using Test containers and layered Docker Compose profiles.
• Collaborate closely with Composer and AI/KB teams on execution semantics and runtime behavior.
• Write clear operational documentation and runbooks for a reliability-critical service.

Qualifications

• Strong production Kotlin backend experience.
• Strong Spring Boot experience in distributed systems or platform services.
• Hands-on Temporal experience in production.
• Strong understanding of workflow durability, retries, idempotency, and recovery design.
• Experience with multi-module Gradle codebases and contract-first API design.
• Experience with JPA/Hibernate and PostgreSQL.
• Experience with Docker Compose/Test containers integration testing.
• Comfort debugging multi-service systems with mixed Kotlin and Python components.
• Experience with observability tools like micrometer
• Experience with contract first development
• Advanced English is required for this position.

Strong Pluses

• Experience with DAG/workflow/orchestration engines.
• Experience with AI/LLM/agent runtimes or other non-deterministic execution systems.
• Familiarity with FastAPI-based workers and cross-language integration.
• Experience with auth/token provider abstractions, OAuth2/JWT, or cached token acquisition.
• Experience writing operational docs, runbooks, and reliability guidance.

Location

Argentina, Peru, Mexico.