SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3d904730aacb91a1366557e92e058fb33c2894001f25492872d7e801ccc8947c' 
  AND token = 'gXOfTxNAND8Bw9ZJqO+7snsReoxDmiQGBt2o0Fbeyyg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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