Instagram: 13 bit shard ID, 51 bit "local" ID consisting of 41 bit timestamp in milliseconds and 10 bit sub-millisecond ID. So this scheme supports 1024 IDs per millisecond per shard for 41 years, and 8192 shards.

Pinterest: 16 bit shard ID, 10 bit type ID(?), 36 bit local ID, 2 bits reserved. This supports 68 billion objects per shard and 65K shards, but does not represent time. So you need another field / more storage for that. Also notable is the large 10 bit type ID field which seems to be only actually used for a handful of values, leading to a large chunk of bits that don't change across IDs.

In short, Instagram's scheme is more efficient largely due to the leverage of timestamps in the ID instead of type information.