Portrait of Bat

Bat-Orshikh Baatar

Senior Software Engineer Java and distributed systems

I build backend services for high-traffic e-commerce, including eBay category pages averaging over 100 million hits a day.

Download resume

Selected work

  1. SEO landing pages at scale

    Problem
    Every one of eBay’s hundreds of millions of search-engine landing pages depends on URL rules that backend services generate and publish to production.
    What I built
    Designed, built and launched the microservices behind those pages, redesigned the URL library’s caching, and restored the publishing pipeline after a network change blocked every SEO, search and item-page team.
    Result
    Category pages alone average over 100M hits a day.
    • Java
    • Spring Boot
    • Microservices

  2. Sticky filter chips

    Problem
    On mobile web, the filter chips scrolled out of view as soon as shoppers reached the results.
    What I built
    Took the spike and the A/B test for chips that stay pinned while scrolling, then owned the launch to all mobile-web traffic and the code cleanup.
    Result
    GMB up 18.07% and transactions up about 15% in the top four markets.
    • A/B testing
    • Java
    • MarkoJS

  3. Product pages on GraphQL

    Problem
    The team needed evidence that GraphQL could match the existing REST backend before moving product pages over.
    What I built
    Developed a GraphQL product-page backend on Spring Boot and Netflix DGS in about six weeks, then load tested it against REST.
    Result
    Same p95 latency as REST with 40% less CPU.
    • GraphQL
    • Netflix DGS
    • JMeter

  4. Cost-per-click ads test

    Problem
    Cost-per-click ads were blocked on category pages, and the ads team wanted to test them there.
    What I built
    Led the backend, writing the design, building click tracking, and finding and fixing a missing experiment header before the test ran.
    Result
    Ads revenue up about 5%, five times the forecast, roughly $2.2M a year annualized. Launch is on hold for a retest.
    • Experimentation
    • Java
    • REST

  5. An agentic AI pipeline for shipping code

    Problem
    Every feature request turned into a spike document, then tickets, then code, then reviews.
    What I built
    Built a pipeline on Claude Code and a Jira MCP server that turns spike documents into tickets and takes each ticket to a pull request, with CLAUDE.md context files for each backend service.
    Result
    Every pull request of my final year at eBay shipped through it.
    • Claude Code
    • MCP
    • Automation

Experience

  1. 2025 — 2026

    Member of Technical Staff 1 · eBay

    San Jose, CA

    Migrated the category-page listings grid to a GraphQL page platform across 10+ sites, built embedding-similarity retrieval for review highlights at a 99.75% SLO, and designed price ranges for trading-card variants that lifted conversion about 16%.

    • Java
    • Spring Boot
    • GraphQL
    • Kubernetes
    • Claude Code

  2. 2023 — 2025

    Software Engineer 3 · eBay

    San Jose, CA

    Led the backend for an ads test that raised ads revenue about 5%, moved a monolithic category-page backend onto a shared listings microservice, and delivered EU Digital Services Act compliance on time.

    • Java
    • Netflix DGS
    • GraphQL
    • JMeter

  3. 2020 — 2023

    Software Engineer 2 · eBay

    San Jose, CA

    Launched sticky filter chips (+18.07% GMB), more than doubled filter usage on eBay Motors, and owned about 20 biweekly backend releases end to end.

    • Java
    • Spring Boot
    • Python
    • MarkoJS

  4. 2019

    Software Engineer · Trade and Development Bank

    Ulaanbaatar, Mongolia

    Built backend and frontend features for internal banking systems and a credit-scoring system.

    • Spring Boot
    • AngularJS
    • PHP

  5. 2017 — 2019

    Full Stack Developer · Asterisk Technologies

    Ulaanbaatar, Mongolia

    Built and supported web applications and ERP projects for clients.

    • Python
    • JavaScript

Education

  • Master's, Computer Science, Maharishi University of Management, Iowa2019 — 2021
  • Bachelor's, Software Engineering, National University of Mongolia2014 — 2018

Full resume (PDF)

About

Bat on the San Francisco Bay at dusk, with the city skyline behind

I'm Bat. I started my career in Ulaanbaatar, Mongolia, building web apps and ERP systems at Asterisk Technologies while finishing a software engineering degree at the National University of Mongolia. I then built banking and credit-scoring software at Trade and Development Bank.

In 2019 I moved to Fairfield, Iowa, for a master's in computer science, and in 2020 I joined eBay. Over six years there I grew from Software Engineer 2 to Member of Technical Staff, working on the backend for category, search-landing and product pages.

The work I like most is where scale meets the shopper, like a latency budget, an A/B test, or a migration that has to land without anyone noticing. Lately that includes building AI agents into how code gets shipped.

Contact

I'm looking for my next senior software engineer, full-stack or AI platform role.

bat.orshikh.baatar@gmail.com