SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'dff3e74547c5b90330ba5ef4343313e3ad1376aff3c0a1e1ea3335b6ce23b451' 
  AND token = 'b5SCbMni/UWqNMD2ZaQLDcz5ULNLCElfHmf+aXj2Feg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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