Depending on what features you are after from the Iglu repository it may be easiest using the static “codeless” repository that is just hosted on S3. You can very easily deploy this (and the other repositories for that matter) without being tied to any other part of the pipeline and use boto3 to interact with it.
That said - I’d strongly recommend deploying the Iglu schema repository in tandem with the other Snowplow components for either batch or real time. They are highly complementary not just from a technical perspective but also a philosophical perspective (in terms of strictly typed, structured data).