Can Bitcoin blocks be organized into shards? Bitcoin Scalability is a hot topic.  In database architecture design data is segmented into shards or the data is partitioned such that it can be spread among large number of machines.

In the financial world, credit card companies like Visa have to deal with thousands of transactions per second.  To deal with this volume credit card processors will use the Date as a shard key.  This allows for the credit card processor to group all transactions made in a set period of time and a set of machines are made responsible for a month of transactions.   Is this sharding tactic compatible with Bitcoin blocks?   Or more generally what if Bitcoin was as popular as credit cards?  What kind of techniques would Bitcoin be forced to use to cope with the scale of the problem?
If you mean whether block verification can be distributed so that one entity can participate without storing the entire blockchain, this isn't compatible with the current design, but maybe a new design can do that. Also, suggestions such as this aim to improve the ability of lightweight (SPV) clients, who do not store the entire blockchain, to verify transactions concerning them specifically, without changing the core protocol.

If you mean whether a single entity can distribute the blockchain among several machines on the same LAN, then this is possible. The basic operation needed for block verification is to look up the details of a previous output, so the natural sharding key would be output hashes. One could also cache the newest outputs which are the most likely to be used in the following transactions.