Senior Kotlin/Spring Boot Engineer at Phoenix, AZ (Onsite)

Tech Mirrors; Phoenix (AZ); On-site; USD 140,000 - 190,000; Full time

Job summary

Tech Mirrors in Phoenix, AZ is seeking a Senior Kotlin/Spring Boot Engineer to own the execution backbone of a no-code workflow platform. You will design and harden the runtime that executes workflow graphs, persist state with Temporal, and coordinate across HTTP, agent, LLM, and human-review nodes in a multi‑module system.

You will implement durable, retry‑resilient services, strengthen contract‑first APIs, and drive reliability with tests, Docker Compose profiles, and observable metrics.

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.

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 Engineer

Kotlin

Spring Boot

Temporal

Tools

Docker Compose

Test containers

Gradle

JPA/Hibernate

PostgreSQL

Micrometer

Job description

Position: Senior Kotlin/Spring Boot Engineer

Location: Phoenix, AZ (Onsite)

Duration: Long term C2C

Skills: Kotlin Engineer, Kotlin, Spring boot, Temporal

Job Description:

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 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.

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

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.