SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6d2c83ad7bd3b8487c7ab527420d98c74a1f4644f522869180a6a4d73914e2ee' 
  AND token = '2MCctOG2POgjjyjZlGnOaMEEYjRneZYUTXhkA/XdBP8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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