3D layers such as integrated meshes, point cloud, 3D object, or buildings are increasingly used in ArcGIS. The size of the data can vary from a small drone flight for a construction site to statewide, countrywide, or global data. ArcGIS provides different workflows to optimize the creation of 3D layers.

You can distinguish between cache-only 3D layers and 3D layers that keep the connection to the origin source. Cache-only 3D layers can be packages like scene layer package (.slpk) or 3D tiles package (.3tz). You can upload cache-only 3D layer and if needed replaced.
In case of a scene layer with associated feature layer you can edit the features and rebuild the cache, based changes made in the feature layer. In addition, you can use capabilities such as search. Since the scene layer with an associated feature layer acts as a unit combining the fast rendering of the scene layer with the capabilities of the feature layer, like search.

Which data representation is best for you depends on the size and type of the 3D layer as well as the capabilities you require. Here are the workflows for ArcGIS Online or ArcGIS Enterprise for 3D web layers.

Large 3D layers in ArcGIS Online

In ArcGIS Online, you can upload a packaged 3D layer such as a scene layer (.slpk) or 3D tiles layer (.3tz). For hosted 3D layer, you only use credits for the storing the package and layer content.

If you work with feature-based scene layers—such as points, 3d object, or building—you can create a scene layer with associated feature layer. You can work with the scene layer in Scene Viewer, ArcGIS Pro, or ArcGIS Maps SDK applications. This type of scene layer can be queried and edited. Scene layers with associated feature layers use credits for the scene layer and associated feature layers.

The following 3D layers can be hosted in ArcGIS Online.

Upload scene layer package (.slpk)

You can create scene layer packages for layer types like integrated mesh, 3D objects, point cloud, voxel, and building scene layer. Choose this workflow if the package is not larger than 500 GB. To save storage space, you can delete the scene layer package item after publishing.
Publish the scene layer from ArcGIS Pro and cache locally if your data is larger than 500 GB. If you cache locally, a scene layer package will be created on your local machine, uploaded to ArcGIS Online, and published.

Scene layer with associated feature layer

You can share scene layers in ArcGIS Pro. You can configure the scene layer properties to cache online. If you cache online, a scene layer with associated feature layer is created. Use this option if you plan to query or edit the features. Another workflows you can use is uploading a zipped file geodatabase containing a mulitpatch or 3D object feature layer. You can publish the feature layer first and than publish the scene layer.
Edit the scene layer with an associated feature layer in ArcGIS Pro. In case you created 3D object scene layers from a 3D object feature layer  you can additionally edit in Scene Viewer.

Upload 3D tiles package (.3tz)

You can create a 3D tiles layer to ArcGIS Online representing data like integrated meshes or 3D objects. You can work with 3D tiles layers in ArcGIS Pro, Maps SDK application, or add  integrated mesh type 3D tiles layer to Scene Viewer.

Large 3D layers in ArcGIS Enterprise

In ArcGIS Enterprise, the recommended workflow is to reference 3D content for scene layers (i3s). The ready-to-use data can be on the file system as ESLPK or in an object store as I3SREST.

I3SREST and ESLPK were introduced in 10.8.1. Since then, many improvements have been made to simplify the creation of extracted caches. You should use extracted caches if your data is larger than 500 GB.
You can use the i3s converter to extract scene layer packages or create scene layers using geoprocessing tools in ArcGIS Pro 2.9 and later. Publish the extracted cache using ArcGIS Pro or via a Python script to create a scene layer.

ESLPK

You can use ESLPK to persist the 3D data in the filesystem of your ArcGIS Enterprise deployment. This workflow is best suited if you are using ArcGIS Enterprise for Windows or Linux, and you are not using cloud storage.

i3sREST

Alternately you can create ready-to-use content for cloud storage, use i3sREST. Select the i3sREST dataset in your registered cloud data store and create a layer item. This workflow is recommended if you are using object store on ArcGIS Enterprise for Windows, Linux, or Kubernetes.

Scene layer with associated feature layer

You can publish multipatch features as a 3D object scene layer and a point feature layer as a point scene layer since ArcGIS Enterprise 10.5. If you require a building scene layer, you will need ArcGIS Enterprise 10.7 or later.  When you plan to work with 3D object scene layer with associated 3D object feature layer you need ArcGIS Enterprise 11.2 and later. Use a scene layer with an associated feature layer if you plan to regularly update attributes or geometries of individual features, or if you want to query the scene layer.

Conclusion

ArcGIS provides different workflows to optimize the creation of 3D web layers. You will have to base your decision on the layer type and if you are hosting the layers in ArcGIS Online or referencing a dataset in ArcGIS Enterprise. Your decision will be influences by the ArcGIS Enterprise version and deployment. Do you want to learn more about 3D layers? Check out 3D workflow resources.