Your MT5 broker, over plain HTTP.

brokers:
  exness:
    type: mt5
    gateway_url: ${QKT_BROKER_EXNESS_GATEWAY_URL}

qkt reaches the broker through the gateway, at this address. The broker's name here is the prefix your strategy uses, like EXNESS:EURUSD. qkt waits for the gateway to report ready before it trades.

Source: mt5-gateway/docs/connect/qkt.md

curl -X POST http://localhost:5001/order \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer $API_KEY" \
  -H "Idempotency-Key: strategy-a-20260703-0001" \
  -d '{"symbol": "EURUSD", "volume": 0.01, "type": "BUY"}'

{"ok": true, "message": "Order placed successfully", "result": {...}}

The same Idempotency-Key and request replay the first answer, so a retry never places a second order. The same key with different parameters is a 409. A 502 unknown_outcome means the broker may have accepted it: check positions before retrying.

Source: mt5-gateway/README.md (the order example and its notes)

app/
├── routes/            Flask routes, one file per resource
├── pretrade.py        safety controls
├── kill_switch.py
├── idempotency.py
└── mt5_connection.py  the one serialized client into the terminal

Every call into the terminal goes through a single serialized client, because MetaTrader 5's Python API is not safe for concurrent access. That is why each broker account gets its own gateway container.

Source: mt5-gateway/docs/concepts/architecture.md

curl -H "Authorization: Bearer $API_KEY" http://localhost:5001/get_positions
curl -H "Authorization: Bearer $API_KEY" "http://localhost:5001/reconcile?magic=12345"

Positions, orders and recent deals can always be read back. When an order's outcome is unknown, that is how you find out what the broker did.

Source: mt5-gateway/README.md