Prev Next

Database / CouchDB Interview Questions

What is Couchbase Sync Gateway and how does it relate to CouchDB's replication model?

Couchbase Sync Gateway is the replication middleware layer in the Couchbase mobile stack. It sits between mobile clients running Couchbase Lite (the embedded mobile database) and a Couchbase Server cluster, handling authentication, authorization, and document routing. Historically it implemented a subset of the CouchDB replication protocol so that CouchDB-compatible clients could sync against it, but Couchbase has since moved toward its own DCP-based (Database Change Protocol) sync approach in newer versions.

The relationship to CouchDB's replication model:

  • Early versions of Couchbase Sync Gateway exposed a CouchDB-compatible REST API and replication endpoint. This meant PouchDB could sync to Sync Gateway using exactly the same protocol it uses with CouchDB.
  • Sync Gateway adds access control channels — each document is tagged with channels and each user is granted access to specific channels. This is a layer that CouchDB itself does not provide natively (CouchDB's access control is at the database level, not document level).
  • From Couchbase Mobile 3.x onward, Couchbase Lite uses a proprietary BLIP WebSocket protocol (not the CouchDB HTTP replication protocol) for sync, diverging from CouchDB compatibility.

For CouchDB users, Sync Gateway is mainly relevant as a comparison point: if you need per-document access control with mobile sync, Sync Gateway's channel model is a more mature solution than CouchDB's validate_doc_update-based approach. Pure CouchDB users achieve similar results by combining PouchDB sync with per-user databases or filtered replication.

What was the historical relationship between early Couchbase Sync Gateway and the CouchDB replication protocol?
What access control feature does Couchbase Sync Gateway provide that standard CouchDB replication lacks natively?

Invest now in Acorns!!! 🚀 Join Acorns and get your $5 bonus!

Invest now in Acorns!!! 🚀
Join Acorns and get your $5 bonus!

Earn passively and while sleeping

Acorns is a micro-investing app that automatically invests your "spare change" from daily purchases into diversified, expert-built portfolios of ETFs. It is designed for beginners, allowing you to start investing with as little as $5. The service automates saving and investing. Disclosure: I may receive a referral bonus.

Invest now!!! Get Free equity stock (US, UK only)!

Use Robinhood app to invest in stocks. It is safe and secure. Use the Referral link to claim your free stock when you sign up!.

The Robinhood app makes it easy to trade stocks, crypto and more.

Webull! Receive free stock by signing up using the link: Webull signup.

More Related questions...

What is Apache CouchDB and what makes it different from relational databases? What data model does CouchDB use and how is a document structured? What is the CouchDB HTTP REST API and how do you perform basic CRUD operations? What is MVCC (Multi-Version Concurrency Control) in CouchDB and how does it handle write conflicts? What is the _rev field in CouchDB and why is it required for updates and deletes? What is the CouchDB storage engine (B-tree) and how does its append-only write work? What is database compaction in CouchDB and when should you run it? What are CouchDB attachments and when would you use them? What is the difference between CouchDB and Couchbase? What are the CAP theorem trade-offs for CouchDB — is it CP or AP? What are CouchDB design documents and what do they contain? What are MapReduce views in CouchDB and how do you define a map function? How does the reduce function work in CouchDB views and what are the built-in reduce functions? What are view indexes in CouchDB and how are they built and updated, including stale options? What is the Mango query language in CouchDB and how does it differ from MapReduce views? How do you create and use a Mango index in CouchDB (json and text indexes)? What are the query operators available in the Mango selector syntax? What is the _all_docs endpoint in CouchDB and how does it differ from a custom view? How do you paginate results in CouchDB views using startkey, endkey, and skip/limit? What is a list function in CouchDB and when would you use it? How does CouchDB replication work and what is the replication protocol? What is the difference between one-shot and continuous replication in CouchDB? What is filtered replication in CouchDB and how do you implement it? What is CouchDB Cluster mode (CouchDB 2.x+) and how does it differ from single-node CouchDB 1.x? How does CouchDB cluster sharding work — what are the Q, n, r, and w parameters? What is the _node and _cluster_setup API used for in CouchDB clustering? How does CouchDB handle replication conflicts and what strategies exist to resolve them? What is the CouchDB winning revision algorithm for conflict resolution? What is PouchDB and how does it enable offline-first applications with CouchDB sync? What is Couchbase Sync Gateway and how does it relate to CouchDB's replication model? How does CouchDB implement authentication — cookie auth, JWT, and proxy auth? What is CouchDB's permission model — admin party, database admins, and database readers? How do you implement document-level security in CouchDB using validate_doc_update functions? What is a CouchDB _security object and how do you configure roles and members? How do you enable SSL/TLS in CouchDB and what configuration is required? How do you monitor CouchDB performance using the _stats and _active_tasks endpoints? What are the key CouchDB configuration parameters to tune for production (max_dbs_open, os_process_limit, etc.)? How does CouchDB handle large document sets — what are the performance trade-offs of large vs many small documents? What is the CouchDB _changes feed and how do you use it for real-time event streaming? What are CouchDB update handlers and how do they differ from direct PUT operations? What are CouchDB show functions and when were they deprecated? How do you back up and restore a CouchDB database? How does CouchDB compare to MongoDB for document storage use cases? What are common CouchDB anti-patterns and how do you avoid them? How do you migrate data between CouchDB versions or instances?
Show more question and Answers...

MuleESB

Comments & Discussions

Interviews Questions

About Javapedia.net

Javapedia.net is for Java and J2EE developers, technologist and college students who prepare of interview. Also this site includes many practical examples.

This site is developed using J2EE technologies by Steve Antony, a senior Developer/lead at one of the logistics based company.

contact: javatutorials2016[at]gmail[dot]com

Kindly consider donating for maintaining this website. Thanks.

Copyright © 2026, javapedia.net, all rights reserved. privacy policy.

DMCA.com Protection Status