CBDH Performance Monitoring & Optimization 4

Question 1

Which state database choice generally gives faster simple key lookups but no rich queries?

Accepted Answer

LevelDB

Answer

LevelDB is embedded and fast for key and range operations but does not support JSON rich queries.

Question 2

Where should CouchDB index definitions be packaged in a Go chaincode so they deploy automatically?

Accepted Answer

META-INF/statedb/couchdb/indexes

Answer

Index JSON files placed in META-INF/statedb/couchdb/indexes are installed with the chaincode package.

Question 3

Why are key-range queries preferred over rich queries when possible?

Accepted Answer

They efficiently scan keys and are re-validated at commit, unlike rich query results

Answer

Range queries are cheaper and their results are re-checked for phantom reads at validation, while rich queries are not.

Question 4

What is the purpose of GetQueryResultWithPagination?

Accepted Answer

Limit the number of results returned per call to bound resource use

Answer

Pagination returns a page of results with a bookmark, preventing huge result sets.

Question 5

Many transactions update a single counter key and most fail with MVCC_READ_CONFLICT. What design change helps?

Accepted Answer

Store each update under a unique composite key and aggregate on read

Answer

Writing separate delta keys avoids multiple transactions in a block contending for one key version.

CBDH - Certified Blockchain Developer Hyperledger Practice Test