A Logstash developer specializes in using the Logstash tool, a server-side data processing pipeline that ingests data from multiple sources simultaneously, transforms it, and then sends it to a preferred "stash" like Elasticsearch. They handle tasks like configuring Logstash to collect, parse, and filter logs from various sources. They are responsible for developing and implementing data transformation rules, debugging and resolving issues, maintaining the pipeline's efficiency and reliability, and ensuring the seamless integration of Logstash within a broader data or IT infrastructure. They also work closely with other team members to optimize data processing and analysis.