Hello Permify team,

While working with multiple tenants, I noticed that some queries in the codebase could be significantly more efficient if composite indexes were added.

1. Function DataReader.HeadSnapshot
   The following query is used:

	builder := r.database.Builder.Select("MAX(id)").From(TransactionsTable).Where(squirrel.Eq{"tenant_id": tenantID})

For optimal performance with large datasets and multiple tenants, a composite index on the transactions table is recommended:

CREATE INDEX CONCURRENTLY IF NOT EXISTS idx_transactions_tenant_id ON transactions (tenant_id, id);

2. Function SchemaReader.HeadVersion
   The following query is used:

	query, args, err = r.database.Builder.
		Select("version").From(SchemaDefinitionTable).Where(squirrel.Eq{"tenant_id": tenantID}).OrderBy("version DESC").Limit(1).
		ToSql()

This would benefit from a composite index on the schema_definitions table:

CREATE INDEX CONCURRENTLY IF NOT EXISTS idx_schema_tenant_version ON schema_definitions (tenant_id, version);

Thank you for considering this improvement!
If needed, I can prepare a PR for this.