Google Maps Directions API integration: route previews, live tracking and what each call costs

How do you integrate Google Maps Directions API, step by step?

1. 1

   Put every Google web-service call behind your backend

   Pakka's apps never call the Directions or Places web services themselves. The mobile backend does, so the server key stays on the server, every answer can be cached and every billable call can be counted. The phones hold only an app key restricted to each app's package name and signing SHA-1; the server key is restricted by IP address.

2. 2

   Cache quotes, not movement

   The Directions cache keys on origin, destination and waypoints rounded to five decimal places and keeps each answer for 10 minutes, so the route preview, the fare quote and the driver's first route share one billed call. Reverse geocodes are kept for 7 days. Business-portal lanes are cached for 30 days: one paid call per lane, not per quote.

3. 3

   Decide when a drawn route is actually wrong

   The apps fetch a route on a leg change (pickup to drop) or when nothing is drawn yet, and refetch only when the driver is more than 150 m from the line, measured to the nearest segment, at most once every 30 seconds. Movement alone never triggers a call from the apps. The rule is one pure function in a file that is byte-identical in the customer and driver apps.

4. 4

   Count the ETA down on the phone

   Instead of asking Google again for a fresh ETA, each app derives the leg's average speed once from the distance and duration the route came back with, applies it to the distance left along the line, and trims the line to the road ahead.

5. 5

   Move the driver's dot over your own socket

   The driver app sends its position after 20 m of movement, at most every 10 seconds, and the server relays it to the booking room over Socket.IO.

6. 6

   Log every billable call with its price

   Each call the mobile backend's maps wrapper sends to Google writes a [maps-billable] log line with its approximate cost in paise. The wrapper warns once per boot when 25 Directions calls have run uncached because Redis is down, or 25 Places calls have arrived without a session token, the two silent multipliers we know about.

7. 7

   Prove the call count with a test

   The test replays a 25-minute drive along a 5 km route, one position every 10 seconds, and asserts exactly one fetch. A negative control sends the driver off route and asserts that it refetches, so a fix that never fetches again cannot pass. Seven more cases pin the edges; all nine pass in both apps.

8. 8

   Check unit prices against a real bill

   Our cost model uses public rates converted at ₹85 to the dollar. Before quoting a per-trip figure outside the team, pull one month from Cloud Billing by SKU and replace the assumed rows.