In the old days of databases, if you put all your data in one place, you could scale up (SMP) but scaling out (MPP) really was challenging. Nowdays, you (iceberg), or a DB vendor (Snowflake, Databricks, BigQuery, even BigTable, etc), put all your data on S3/GCS/ADLS and you can scale out compute to read traffic as much as you want (as long as you accept something like a snapshot isolation read level and traffic is largely read-only or writes are distributed across your tables and not all to one big table.)
You can now share data across your different compute nodes or applications/systems by managing permissions pointers managed via a cloud metadata/catalog service. You can get microservice databases without each having completely separate datastores in a way.