Create a scientific figure about: Microservice system topology with gateway and async messaging.
Visual style: Scientific Engraving Monochrome.
Requirements:
- publication-ready scientific quality
- clear labels and directional arrows where appropriate
- avoid cartoon style, avoid meme style, avoid stock-photo look
- avoid neon glow and over-sharpened CGI look unless explicitly requested
- composition optimized for research papers and academic slides
- category context: systems-networks
- vintage scientific engraving style with fine hatching and contour lines
- monochrome or near-monochrome gray palette with high structural clarity
- plate-like composition similar to historical scientific references
