Ola — Detailed#

flowchart TB
  subgraph Apps
    RAPP([Rider app])
    DAPP([Driver app])
  end

  subgraph Edge
    CDN
    LB
    GW[Edge gateway<br/>per-region]
    WS[WebSocket]
  end

  subgraph Geo[Geo Indexing - hot path]
    LOC([Location Ingest])
    GIDX([(Driver presence<br/>S2 cell / geohash)])
    AVAIL([Available drivers per cell])
    ETA1([Ego-driver ETA estimator])
  end

  subgraph Dispatch[Dispatch / Matching]
    DSVC[Dispatch Service]
    POOL[Candidate pool fetch]
    SCORE[Score: distance, ETA, ratings, surge]
    OFFER([Offer to driver - 15s])
    BATCH[Batch / pool rides]
  end

  subgraph Pricing
    BASE[Base fare]
    SURGE[Surge model]
    EST[Trip estimate]
  end

  subgraph Trip
    LIFE[Trip lifecycle SM]
    NAV[Nav + route]
    TKM([Telematics ingest])
    RECEIPT[Receipt + tax]
    PAYSVC[Payment]
    PG((Payment provider))
  end

  subgraph Safety
    BG[Background checks]
    PIN[Trip PIN]
    SOS[Emergency / panic]
  end

  subgraph Data
    KAFKA[[Kafka event bus]]
    FS[Feature store]
    ML[ML platform]
    OBS[Metrics / traces]
  end

  RAPP --> CDN --> LB --> GW
  DAPP --> LB
  DAPP --> WS --> LOC --> GIDX
  RAPP --> Dispatch
  Dispatch --> Geo
  Dispatch --> Pricing
  Dispatch --> Trip
  Trip --> PAYSVC --> PG
  Trip --> KAFKA
  Geo --> KAFKA --> FS --> ML
  ML --> Pricing
  Safety --- Trip
  OBS --- Dispatch

    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 RAPP,DAPP,AVAIL,ETA1,OFFER client;
    class GW edge;
    class WS,DSVC,POOL,SCORE,BATCH,BASE,SURGE,EST,LIFE,NAV,RECEIPT,PAYSVC,BG,PIN,SOS,ML service;
    class GIDX,FS datastore;
    class KAFKA queue;
    class LOC,TKM compute;
    class PG external;
    class OBS obs;

Geo index#

Driver location every 1-3 s → server.
Index sharded by S2 cell ID; updates write-heavy.
Active drivers stored in Redis-like KV with (driver_id, cell, ts); TTL purges stale.

Dispatch algorithm#

Customer requests ride at point P.
Geo lookup returns drivers in expanding S2 ring around P.
Score each candidate (ETA + last assignment time + ratings).
Offer to top driver; 15 s timeout; on reject, next.
Update driver presence → unavailable on accept.

Surge pricing#

Per S2 cell × minute: demand/supply ratio.
Multiplier applied at quote time; shown to user before confirm.

Trip lifecycle#

States: REQUESTED → DRIVER_ASSIGNED → EN_ROUTE → ARRIVED → IN_PROGRESS → COMPLETED / CANCELLED.
Each transition emits an event; finance + analytics consume.

Glossary & fundamentals#

Concepts referenced in this design. Each row links to its canonical page; the tag column shows whether it is a high-level (HLD) or low-level (LLD) concept.

Tag	Concept	What it is	Page
`HLD`	CDN	edge caching for static assets	cdn
`HLD`	Sharding	horizontal partitioning across nodes	database-sharding
`HLD`	Pub/Sub & message brokers	topics, consumer groups, delivery semantics	pub-sub-pattern
`HLD`	Observability	metrics, logs, traces, SLOs	observability
`HLD`	Realtime protocols	WS / SSE / polling / gRPC streaming	realtime-protocols
`HLD`	Geo indexing	Geohash, Quadtree, S2, H3, R-tree	geo-indexing