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CouchDB vs Scylla: What are the differences?
Introduction:
CouchDB and Scylla are both popular database management systems, but they have several key differences that set them apart. In this comparison, we will explore the specific distinctions between CouchDB and Scylla.
Data Model: CouchDB is a document-oriented database that stores data in JSON-like documents. It is schemaless, allowing flexibility in data structure. On the other hand, Scylla is a wide-column store based on Apache Cassandra, utilizing a data model that organizes data in rows, columns, and tables. It follows a schema-based approach, requiring predefined column families and column names.
Consistency Model: CouchDB follows eventual consistency, which means that the database may not always reflect the latest updates immediately, but it ensures that all updates will be eventually propagated. In contrast, Scylla offers strong consistency by default. It ensures that all replicas of a piece of data are consistent and up-to-date before returning a response.
Replication and Distribution: CouchDB uses master-master replication, allowing data to be synchronized bidirectionally across multiple instances. This enables high availability and fault tolerance. On the other hand, Scylla uses consistent hashing for data distribution and relies on peer-to-peer gossip protocol for replication. It provides linear scalability by adding more nodes to the cluster.
Query Language: CouchDB utilizes MapReduce as its primary query language. It allows users to define map and reduce functions to extract and manipulate data. Scylla, being based on Cassandra, uses CQL (Cassandra Query Language) for querying and manipulating data, which provides a familiar and SQL-like syntax for developers.
Storage Engine: CouchDB employs an append-only B-tree storage engine, where all changes are written sequentially to disk. It ensures durability and immutability of data. On the other hand, Scylla uses its own storage engine called "Seastar," which implements a log-structured merge tree (LSM) for storing and managing data efficiently.
Tunability and Optimal Use Case: CouchDB is often chosen when offline availability, conflict resolution, and a flexible data model are crucial requirements. It is well-suited for use cases like mobile applications and decentralized systems. Scylla, with its high throughput and low latency characteristics, is more suitable for applications that demand massive scalability, real-time analytics, and low-latency operations.
In Summary, CouchDB is a document-oriented database with eventual consistency, while Scylla is a wide-column store with strong consistency. CouchDB uses master-master replication and MapReduce, whereas Scylla utilizes consistent hashing and CQL. They have different storage engines, tunability, and ideal use cases.
The problem I have is - we need to process & change(update/insert) 55M Data every 2 min and this updated data to be available for Rest API for Filtering / Selection. Response time for Rest API should be less than 1 sec.
The most important factors for me are processing and storing time of 2 min. There need to be 2 views of Data One is for Selection & 2. Changed data.
Scylla can handle 1M/s events with a simple data model quite easily. The api to query is CQL, we have REST api but that's for control/monitoring
Cassandra is quite capable of the task, in a highly available way, given appropriate scaling of the system. Remember that updates are only inserts, and that efficient retrieval is only by key (which can be a complex key). Talking of keys, make sure that the keys are well distributed.
By 55M do you mean 55 million entity changes per 2 minutes? It is relatively high, means almost 460k per second. If I had to choose between Scylla or Cassandra, I would opt for Scylla as it is promising better performance for simple operations. However, maybe it would be worth to consider yet another alternative technology. Take into consideration required consistency, reliability and high availability and you may realize that there are more suitable once. Rest API should not be the main driver, because you can always develop the API yourself, if not supported by given technology.
i love syclla for pet projects however it's license which is based on server model is an issue. thus i recommend cassandra
The Gentlent Tech Team made lots of updates within the past year. The biggest one being our database:
We decided to migrate our #PostgreSQL -based database systems to a custom implementation of #Cassandra . This allows us to integrate our product data perfectly in a system that just makes sense. High availability and scalability are supported out of the box.
We implemented our first large scale EPR application from naologic.com using CouchDB .
Very fast, replication works great, doesn't consume much RAM, queries are blazing fast but we found a problem: the queries were very hard to write, it took a long time to figure out the API, we had to go and write our own @nodejs library to make it work properly.
It lost most of its support. Since then, we migrated to Couchbase and the learning curve was steep but all worth it. Memcached indexing out of the box, full text search works great.
Pros of CouchDB
- JSON43
- Open source30
- Highly available18
- Partition tolerant12
- Eventual consistency11
- Sync7
- REST API5
- Attachments mechanism to docs4
- Multi master replication4
- Changes feed3
- REST interface1
- js- and erlang-views1
Pros of ScyllaDB
- Replication2
- Fewer nodes1
- Distributed1
- Scale up1
- High availability1
- Written in C++1
- High performance1