1. FastConnect V3 Service
What FastConnect is, its current API groups, registration requirements/process, the UAT/Production environments, and rate limiting.
What is FastConnect?
FastConnect is SSI Securities' electronic trading API platform, providing REST APIs and WebSocket connections for fintech partners, institutional investors, and third-party developers to trade securities on HoSE/HNX/UPCOM and query market data.
What API groups does FastConnect currently offer?
6 main groups: Authentication (auth, token issuance), Trading (place/amend/cancel orders, account queries), Conditional Orders (FCO) (orders that trigger automatically on market conditions), Market Data (market data over REST), WebSocket (real-time data, push-only), and WebSocket API (place/amend/cancel orders, including in bulk, purely over WebSocket). See the API Reference overview.
What do I need to register for the FastConnect API?
You need an existing securities account at SSI. The FastConnect API is only available to clients who already have a trading account — if you don't have one yet, open an SSI account before registering for API access.
Is there a fee to register and use the API?
SSI currently does not charge for the FastConnect API service.
How does the registration process work, and how long does it take?
Registration and activation happen entirely through the Developer Portal: create a developer account, accept the terms of use, create an API Key, and choose an environment (UAT/Production). The whole flow is online — there's no manual email-based approval wait like before. See Registration for details.
How many API Keys can one account create?
You can create multiple API Keys under one account, each with its own purpose/scope (for example, one read-only key for Market Data and another with Trading permissions) to improve security when running multiple systems.
What's the difference between the UAT and Production environments?
UAT (User Acceptance Test) is for integration and testing without affecting real accounts or data. UAT and Production API Keys are completely separate — you need to register/activate each one independently on the Developer Portal. SSI will notify you once the UAT environment is ready for use.
How does API rate limiting work?
Each API Key has its own quota per endpoint/method. The current quota is returned transparently via the X-RATELIMIT-LIMIT/X-RATELIMIT-REMAINING/X-RATELIMIT-RESET headers on every response — you can monitor and adjust your call frequency based on these headers instead of guessing.