Geo Indexing — Simple#
flowchart LR
P[Point or polygon]
QT[Quadtree]
GH[Geohash]
S2[S2 cells]
H3[H3 hexes]
RT[R-tree]
Q[Spatial query]
P --> QT --> Q
P --> GH --> Q
P --> S2 --> Q
P --> H3 --> Q
P --> RT --> Q
classDef client fill:#dbeafe,stroke:#1e40af,stroke-width:1px,color:#0f172a;
classDef edge fill:#cffafe,stroke:#0e7490,stroke-width:1px,color:#0f172a;
classDef service fill:#fef3c7,stroke:#92400e,stroke-width:1px,color:#0f172a;
classDef datastore fill:#fee2e2,stroke:#991b1b,stroke-width:1px,color:#0f172a;
classDef cache fill:#fed7aa,stroke:#9a3412,stroke-width:1px,color:#0f172a;
classDef queue fill:#ede9fe,stroke:#5b21b6,stroke-width:1px,color:#0f172a;
classDef compute fill:#d1fae5,stroke:#065f46,stroke-width:1px,color:#0f172a;
classDef storage fill:#e5e7eb,stroke:#374151,stroke-width:1px,color:#0f172a;
classDef external fill:#fce7f3,stroke:#9d174d,stroke-width:1px,color:#0f172a;
classDef obs fill:#f3e8ff,stroke:#6b21a8,stroke-width:1px,color:#0f172a;
class P,QT,GH,S2,H3,RT,Q service;
Five spatial-index choices for "nearby" / "within radius" / "in this polygon" queries: Quadtree, Geohash, S2, H3, R-tree. Pick by data shape, query shape, and how sharded the world needs to be.