Core API: The Core API is used for the integration of external applications like Channels, CRM, and External Bureaus etc. It allows you to carry out calls to resources within Vault such as,

Account Management

Product Management 

The Core API

Restrictions

Smart Contract Simulation

Internal Accounts

Payment Devices

Role Management

Flags

Postings API: The Postings API is responsible for managing all financial movements on accounts held within Vault, journeys you’ll use it for include:

Authorization check on accounts.

Settlement of funds on accounts.

Release of funds.

Post credit and debits to Vault

Note: Core API and Postings API is a RESTful synchronous APIs

Streaming API The streaming API provides native support for real-time events streamed

out of Vault according to when something is written to the Vault Database.

Events include Customer Account change events, Accounting events, Posting Balance updates, Customer entity status changes, Payment Device events, External Workflow request/response, smart contract activation, configuration changes, and versioning changes

Note: Streaming

API is Kafka API and asynchronous