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Alex K.
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Alex K.

AI & Backend Engineer | LLM agents, Harness, Cloud-Native Backends

I am a Senior Software Engineer focused on backend systems, LLM agents, and developer automation. My main specialization is building reliable agent harnesses: the engineering layer around LLMs that handles tools, context, workflows, validation, retries, structured outputs, API integrations, and production behavior. I work primarily with Java, but I also use Rust, Go, and Python for infrastructure, automation, performance-sensitive components, and AI-related systems. I have strong hands-on experience with modern coding agents and AI engineering tools. I use Codex, Claude Code, and Gemini in my daily development workflow, and I understand how to use them effectively for task decomposition, implementation, code review, testing, refactoring, and debugging. I have also worked with Cursor and Antigravity, and I am familiar with OpenClaw, Hermes, and similar agent architectures. I am the author of golemcore-bot, an LLM harness project focused on practical agent runtimes and automation systems. I have also worked on multiple specialized harnesses for LLM-based workflows involving tool execution, context management, structured outputs, API integration, and robust error handling. My background is backend-heavy: Java, Spring, distributed systems, cloud-native services, databases, messaging, Docker, Linux, CI/CD, and production troubleshooting. I value clean architecture, pragmatic testing, maintainable code, and simple designs that can scale without becoming fragile. Technologies I commonly work with include Java, Spring, Maven, Gradle, PostgreSQL, MongoDB, Redis, Kafka, Docker, Git, Linux, AWS, Google Cloud, JUnit, Mockito, Rust, Go, and Python. I can help with backend engineering, LLM agents, coding agents, automation platforms, developer tools, cloud-native services, and production-grade integrations.

🇩🇴Sosua, Dominican Republic$85/hr100% JSS4.97 (17)Since Nov 2014

Earnings and projects

MRR
$15k

Last 6 months ÷ 6

World#498 / 412k
🇩🇴Country#1 / 1,225
Revenue, last 30 days
$14k

Last 6 months: $87k

World#650 / 412k
🇩🇴Country#1 / 1,225
Total earnings
$949k

Billed in all: $993k

World#655 / 412k
🇩🇴Country#2 / 1,225
Per project
$38k

$22k in the last 6 months

World#1,745 / 412k
🇩🇴Country#3 / 1,225
Projects, last 6 months
4
0% fixed100% hourly
World#51,813 / 412k
🇩🇴Country#80 / 1,225
Projects in all
25

Across 31 contracts

65% fixed35% hourly
World#113,042 / 412k
🇩🇴Country#115 / 1,225

Earnings, last 30 days

$993k+$14.3k earned in the last 30 daysBilled in all, before Upwork's fee · drag across the chart to see what was earned in any stretch
$0.97M$0.98M$0.99M$1.00MOct 8Oct 23Nov 7

Skill rankings: #1 in 2 skills of 18

Rarest: top 0.11% in Spring Framework, of 880. Ranked by MRR among everyone on Upwork with the skill.

  1. 1Spring Framework880 freelancers · 🇩🇴 #1Top 0.11%
  2. 1Apache Cassandra82 freelancers · 🇩🇴 #1Top 1%
  3. 2Apache Kafka981 freelancers · 🇩🇴 #1Top 0.20%
  4. 2Amazon DynamoDB464 freelancers · 🇩🇴 #1Top 0.43%
  5. 3Elasticsearch946 freelancers · 🇩🇴 #1Top 0.32%
  6. #6Golang2,195 freelancers · 🇩🇴 #1Top 0.27%
  7. #6Rust888 freelancers · 🇩🇴 #1Top 0.68%
  8. #11Java8,313 freelancers · 🇩🇴 #1Top 0.13%