Greg's response correctly deals with the greater issue that the sync time implies that you have something overloading the sync which affects your total time and the sync of a given object's updates (at my current org we've dealt with certain usage fields overloading the Account Sync), to fix the immediate problem of needing to get a high value lead into SFDC and the sales person's hands, you can use a flow step labeled "Sync Person to SFDC" (Docs site link) that skips the normal sync cycle. You'd want to use this only in a centralized campaign and sparingly, as it does take up a lot of resources relative to other updates, but for those super high priority leads this is a way to hotfix while you deal with the other sync issues. If you're an org that creates a new lead regardless if the person already exists in the system, this is also how that's accomplished.
Thanks Oliver. That makes sense.
Another question - when using "Sync Person to SFDC", will the leads be synced at the campaign level as well? Having the leads associate with a campaign with proper status is the key to our lead scoring and lead routing (we use Full Circle Insight response management package to MQL; and only MQLs will be routed to sales).
No problem, as to the campaign sync (caveat: not sure on this) I believe it will for systems using the Campaign-Program level sync but for other instances, it would depend on the SFDC customizations - I've only ever used the flow step in this manner with a heavily customized campaign attribution setup so my experience wouldn't be indicative of the norm.
if campaign sync is activated in the admin, yes. But they can be many and explain the overload.
Really impressed with the thoroughness of your post here Gregoire Michel. I may have missed it, but adding in functionality to sync SFDC Person Accounts would be a helpful addition as well.
Sync'ing person accounts is already possible, though it could be enhanced. The default of the person account sync is that Marketo continues to sync account and contact data as if they were separate. You need in the Marketo admin interface to go an hide account fields that contain values that are identical to the contact ones. Of course, you should only do this if you only use person accounts in SFDC. If you are in a mixed environment, hiding account fields is not relevant.