SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b6ae98411c4092cb6cd9df34cacd931795f1e49d8551e7fa00b48a3f99b4dcf6' 
  AND token = 'n9KtFO9xrXL3BuRwc4RMPR6mVgTehPLxll6N2VD+ds4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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