SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c91b9864aee3501a591b76ed24481c400fc4a528dbf0858fe743efc4cc5df351' 
  AND token = 'kXsnTt4WKrbbhfhE1boKI7Ezu8hyGbN5eYMEt7It72c=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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