SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '84fe3c31b20816292fa1332a39c2441854f7083236a5e150473b4cfe4652a386' 
  AND token = 'OubiMdBd8XDMRwojpnU1F/d7P7JCGPXfLvgP/a+wnM0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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