[BUG] createInstance massive slowdown

[fooku18]

Is there an existing issue for this?

• I have searched the existing issues

SDK Version

6.0.0

Current Behavior

We have observed a significant slowdown in the createInstance function since the latest major release, v6. Previously, this function executed in an average of a few milliseconds when provided with a string datafile, as outlined in the configuration documentation. The use of a string datafile is supported for both project config managers, createPollingProjectConfigManager and createStaticProjectConfigManager, as described in the API. Benchmark results indicate the following average execution times:

v5: createInstance 6.4ms
v6: createInstance 130.5ms

I added additional timing logs to identify the bottleneck, and it appears that this forEach loop, which constructs the experiments, accounts for the majority of the time taken by createInstance.

In our case, we provide a stringified version of the datafile because we resolve it during server-side rendering (SSR), making it redundant to fetch the file again during browser initialization. The extent of the slowdown is substantial enough that I consider this a bug.

Expected Behavior

Similar time as with v5.

Steps To Reproduce

Run createInstance and measure timings

SDK Type

Node

Node Version

v22.18.0

Browsers impacted

all

Link

No response

Logs

Severity

Affecting users

Workaround/Solution

No response

Recent Change

No response

Conflicts

No response

[raju-opti]

Hello @fooku18 , thank you for reporting the issue. We have created internal ticket FSSDK-11787.

[raju-opti]

Hello @fooku18 , a follow up questions, can you tell approximately how many experiments are there in the datafile you are using?

[raju-opti]

I think we have found out the cause of the slowdown. we'll be releasing a patch version soon