SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '75e99192a96b0a510520874bffdcecc9e0eef5caf550fa9db9389cdcf1c5747b' 
  AND token = '/ZRtJ9FaS2GPkUNwwgD/Z/hGAWEK+tyqAJGvVO2yVHw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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