[Metrics] Improve OD → ND Transition Performance

[rlinoz]

Objective

We want to improve the OD → ND Transition performance metric.

Target: 3 seconds

You can check the current values and monitor progress at:
https://expensify.sentry.io/dashboard/166516/?environment=adhoc&environment=dev&environment=development&environment=production&environment=staging&statsPeriod=7d

[rlinoz]

Waiting for someone to pick this up.

[elirangoshen]

Hi, I can work on it

[melvin-bot]

@rlinoz, @elirangoshen Eep! 4 days overdue now. Issues have feelings too...

[melvin-bot]

@rlinoz, @elirangoshen Still overdue 6 days?! Let's take care of this!

[melvin-bot]

@rlinoz, @elirangoshen Now this issue is 8 days overdue. Are you sure this should be a Daily? Feel free to change it!

[elirangoshen]

Im still working on it

[elirangoshen]

I would like to share some of my findings about the performance of that process along with one idea I had and maybe you can let me know what do you think.

This is the the main 2 longest actions as I debug it with big test account , in Session/index.ts

I converted the functions to async to be easier to debug:

      await HybridAppActions.prepareHybridAppAfterTransitionToNewDot({
            ...hybridApp,
            closingReactNativeApp: false,
        });

this one takes around 1000-2500ms in our big account

await Promise.all(Object.entries(newDotOnyxValues).map(([key, value]) => Onyx.merge(key as OnyxKey, value ?? {})));

newDotOnyxValues usually contains in our account this data:

{
  "shouldUseStagingServer": false,
  "nvp_tryNewDot": {
    "classicRedirect": {
      "dismissed": false,
      "dismissedReasons": [
        {
          "reason": "",
          "timestamp": "2025-12-05 06:44:55.351"
        }
      ],
      "timestamp": "2025-12-29T11:13:27.644Z"
    },
    "tappedTryNewExpensifyButton": {
      "timestamp": "2025-12-29T11:13:27.644Z"
    }
  }
}

this one takes around 700ms to execute

One lead I tried is to execute both of the operations in the same time :

await Promise.all([
            HybridAppActions.prepareHybridAppAfterTransitionToNewDot({
                ...hybridApp,
                closingReactNativeApp: false,
            }),
            Promise.all(Object.entries(newDotOnyxValues).map(([key, value]) => Onyx.merge(key as OnyxKey, value ?? {}))),
        ]);

This improves a lot the total duration (in around 1.5-2 seconds) but i'm not sure if its ok to not wait for prepareHybridAppAfterTransitionToNewDot to finish before executing the other merge operations.

What do you think ?

@rlinoz @sosek108

[rlinoz]

It doesn't look like they merge the same keys in Onyx, so I think it should be ok to run them in parallel, but why do they take so long?