Investigate API rate limits on feature_flags/unleash

Problem to solve

The feature_flags/unleash endpoint has been rate limited, we should evaluate rate limiting rules on this endpoint to establish if they need to be adjusted.

The following (internal) dashboard was used: https://log.gprd.gitlab.net/goto/e25a5ff9c1279056c2fd3c1713e15b9a

Details

filters	filters	json.meta.caller_id.keyword: Descending	Count	Percentage of rate limited	Percentage matching filter
json.path : "feature_flags/unleash"	Rate limited	Not recognized because limited	5,150,096	53.78%	2.35%
json.path : "feature_flags/unleash"	Not rate limited	GET /api/:version/feature_flags/unleash/:project_id/client/features	164,037,793		74.79%
json.path : "feature_flags/unleash"	Not rate limited	POST /api/:version/feature_flags/unleash/:project_id/client/metrics	39,306,027		17.92%
json.path : "feature_flags/unleash"	Not rate limited	GET /api/:version/feature_flags/unleash/:project_id/features	7,639,644		3.48%
json.path : "feature_flags/unleash"	Not rate limited	POST /api/:version/feature_flags/unleash/:project_id/client/register	3,195,256		1.46%

What's the action item?

Investigate rate limiting scenarios for this endpoint/set of endpoints and establish what's causing it.

Evaluate existing API rate limits for this endpoint/set of endpoints and implement changes where appropriate.