Dispatch Service

consistent hashing sharded by geohash

data is transient, in memory, and thus there is no need to replicate. (CAP: AP over CP)

single-threaded or locked matching in a shard to prevent double dispatching

Payment Service

==The key is to have an async design==, because payment systems usually have a very long latency for ACID transactions across multiple systems.

leverage event queues

payment gateway w/ Braintree, PayPal, Card.io, Alipay, etc.

logging intensively to track everything

APIs with idempotency, exponential backoff, and random jitter

UserProfile Service and Trip Service

low latency with caching

UserProfile Service has the challenge to serve users in increasing types (driver, rider, restaurant owner, eater, etc) and user schemas in different regions and countries.

Push Notification Service

Apple Push Notifications Service (not quite reliable)

Google Cloud Messaging Service GCM （it can detect the deliverability) or

SMS service is usually more reliable

https://www.geeksforgeeks.org/system-design-of-uber-app-uber-system-architecture/