SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b8e7d45e2cebe0975aecb7ebc9d2b014b9771772305e896117aeaca6adfdbafe' 
  AND token = 'KKpYAyJeEYIXMp2yyGsOGw0qClY8O5AOj3+/02/nrlo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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