OnEarth is NASA GIBS's geospatial tile serving system designed to deploy OGC-compliant web services (WMTS, WMS, TWMS) for raster and vector earth observation imagery. It is a hybrid system that functions primarily as a production-grade application—composed of Dockerized microservices (tile, time, capabilities, reprojection, WMS, demo) backed by Apache HTTPD with custom C modules (mod_mrf, mod_brunsli, mod_convert, mod_twms, mod_wmts_wrapper, etc.) for high-performance tile serving and format transformation. The system also includes substantial data-processing tooling for generating Meta Raster Format (MRF) tiles from georeferenced images, creating vector tiles, managing colormaps, and synchronizing data from S3. The architecture is modular and configurable via YAML endpoint/layer definitions, with temporal layer support managed through Redis and a Python time service. While the codebase shows signs of organic growth over many years—some duplicate utilities and hardcoded paths—it contains well-crafted isolated components that could be extracted for reuse in other geospatial or web-serving contexts.