SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3eb915d2e88bf58f44dc65a9092befcd3a72fcabcbc25683695378e630777028' 
  AND token = 'nQ50MxYRz7LqJrTBeugWiC3EO+PGtwq5WcKlzDtdSjo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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