Genomic Variant Annotation Microservice with Flask

Develop a Flask-based microservice for real-time genomic variant annotation that can rapidly process VCF files and cross-reference against multiple genomic databases. The service must implement efficient caching mechanisms, support parallel processing of large genomic datasets, provide RESTful API endpoints for variant querying, and include comprehensive logging and error tracking. Implement authentication, rate limiting, and the ability to handle variants from multiple genome assemblies (hg19, hg38).