There's replication in ClickHouse and you can just shove reads off to one of them if you'd like. From a backup/safety standpoint that's important, but I think there are other options besides just replicas, of course.
From an operations standpoint, however, ClickHouse is ridiculously efficient at what it does. You can store tens of billions, probably trillions of records on a single node machine. You can query at tens of billions of rows a second, etc, all with SQL. (The only competitor I know of in the same class is MemSQL.) So another thing to keep in mind is you'll be able to go much further with a single node using ClickHouse than the alternatives. For OLAP style workloads, it's well worth investigating.
