Senior Search Platform Infrastructure Engineer

Job Overview

This position is for a Senior Search Platform Infrastructure Engineer at Mercari, a company that operates a marketplace app focused on circulating value to help people realize their dreams. The role is based in Roppongi, Tokyo, with full flextime (no core time) and is part of the Platform Division's Autonomous Cloud group.

Key Responsibilities

• Co-own the Elasticsearch cluster lifecycle: provisioning, sizing, upgrades, shard/replica strategy, and index management for product-critical search workloads.


• Join the search infrastructure on-call rotation after ramp-up; lead incident response, root-cause analysis, and follow-through improvements.


• Drive performance and reliability initiatives across the cluster, JVM, and query layers. Improve the search APIs and aggregation services consumed by product teams.


• Collaborate with the Platform Infrastructure team on high-impact Kubernetes and Terraform changes as a senior reviewer and engineer; mentor engineers across both teams.

Unique Challenges

• Operating a search platform that serves product-critical workloads at very large scale (hundreds of millions of indexed items at sustained high query volume) with demanding availability and latency expectations.


• Owning the full search infrastructure stack end-to-end - from cluster operations and JVM tuning down to query-path performance - across a small, deep team where each engineer has real platform-level ownership.


• Balancing day-to-day reliability of running clusters with longer-horizon investments: version upgrades, automation, and evaluating next-generation search and vector technologies.


• Sitting at the boundary between infrastructure and product - translating between platform-level concerns (capacity, reliability, cost) and product-team needs (indexing patterns, query behavior, search experience).

Required Qualifications

• Shared belief in Mercari's mission and values.


• Senior-level engineering experience operating distributed systems in production at scale.


• Strong system-design and distributed-systems fundamentals: consistency, replication, capacity planning, failure modes.


• Production ownership of Elasticsearch (or a comparable Lucene-based search engine) - cluster sizing, JVM/heap tuning, query-performance debugging, shard strategy.


• Track record of owning a technical domain end-to-end: design, build, on-call, incident follow-through, long-term roadmap.


• Proficiency in Go and/or Java.


• English: Business level (CEFR – B2)

Preferred Qualifications

• Lucene internals or JVM performance-engineering depth.


• Vector search knowledge.


• Production experience operating Kubernetes (GKE, EKS, or AKS) - cluster upgrades, incident debugging.


• Terraform at scale (custom modules, large-blast-radius migrations).


• CI/CD platform experience (GitHub Actions, Jenkins, or similar).


• Search/data services for C2C or e-commerce at scale.

About Mercari

Mercari is a marketplace app that was born in 2013 out of the thought of circulating all forms of value to create opportunities for anyone to realize their dreams and contribute to society. The company aims to use technology to connect people all over the world and create a world where anyone can unleash their potential.