SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6b839812a6ff660413dd965cbc0a63d99500ee6c9cf3acc6ec94fffaae8f4b9f' 
  AND token = '6BdwoU1RbXaGxbFCYfy8TBdP55RLbua51wDTbmMsfNg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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