Sometimes, it can be useful to have one or more tables on each shard with the same data. SPQR supports what are known as reference table. A reference table is replicated across all shards and is not split into separate partitions. Every shard has a local copy of the table, which reduces network overhead and allows for fast access to frequently used data. 
\c spqr-console
CREATE REFERENCE TABLE tax_rates;
         attach table          
-------------------------------
 relation name   -> tax_rates
 distribution id -> REPLICATED
(2 rows)