SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '75012549f7cd9cce0259792261b4045f1ad99ec6545e720909b8d8fc16df1249' 
  AND token = 'zJmbPz2m8oP38gib/hwfj7YxHqw/qa/5RlvFmHvAcjU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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