A GATK (Genome Analysis Toolkit) developer is a bioinformatics professional who works on the development and optimization of the GATK software, a toolset used for genomic variant discovery and genotyping. Their tasks include designing and implementing algorithms for genetic analysis, improving the software's efficiency, and fixing bugs. They also collaborate with researchers to understand their data analysis needs, implement new features, and provide technical support. Moreover, they ensure the software complies with genomic data processing standards and contribute to the development of new methodologies in the field of genomics. They often need a strong background in bioinformatics, programming, and genomics.