SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '35df50eafcfddf5911762decec6c11ec1d6f926f204f56ee272c98636aa8374d' 
  AND token = '9AyYewXJNdK4e2zbKZ7jtf03NvXXPSqAlWfRnB0XCZg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}