Methods, apparatus and computer program product for creating an externally shared communication channel in a group-based communication platform are described herein. The group-based communication platform may have a plurality of database shards. A computer-implemented method may include receiving, from a first client device associated with an initiator group identification, a shared communication channel generation query associated with the initiator group identification and a target group identification; generating, in the group-based communication platform, a shared communication channel shard; transmitting, to a second client device associated with the target group identification, a shared communication channel acceptance request; receiving a shared communication channel acceptance notification; updating, in a main database, a shard referential table based on the initiator group identification, the target group identification, and the shared communication channel identification; and transmitting a shared communication channel interface of the shared communication channel based on the shared communication channel shard.