SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6b5e077a3bb5d368c7243d7caa8697048e5bcecc10390caa843a89ede600233f' 
  AND token = 'KUUtwzKxjqUZ+y5p2h5QgnBUCStCPAAQSacqWwiRefU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}