The document compares Apache Cassandra and ScyllaDB, highlighting that ScyllaDB is a high-performance, low-latency NoSQL database compatible with Cassandra and DynamoDB but designed for better efficiency through its shard-per-core architecture. It discusses evolutionary differences between the two, including software release cycles, performance benchmarks, and community perception, noting ScyllaDB's rapid development and enhancements. ScyllaDB offers features such as a dynamodb-compatible API and improved handling of lightweight transactions, making it a competitive choice for data-intensive applications.

1. Cassandra vs. ScyllaDB:
Evolutionary Differences

2. Peter Corless
+ Listen to customer stories
+ Write blogs & case studies
+ Play (and design) strategy &
roleplaying games
Director of Technical Advocacy
ScyllaDB

3. 3
+ For data-intensive apps that require high
performance and low latency
+ Fully compatible with Apache Cassandra
and Amazon DynamoDB
+ 10X the performance & low tail latency
+ Open Source, Enterprise and Cloud options
+ Founded by the creators of KVM hypervisor
+ HQs: Palo Alto, CA, USA; Herzelia, Israel; Warsaw,
Poland; Teams around the world
About ScyllaDB

4. 4
+ From “Chasing Cassandra” to “Beyond Cassandra”
+ Comparing Open Source Releases
+ Software Release Cycles
+ Public Perceptions
+ Features
+ Same-Same, Similarities, Differences
+ Benchmarks
Comparison: Cassandra vs. ScyllaDB

5. 5
+ Wide-column NoSQL database (“key-key-value”)
+ Originally a re-architected reimplementation of Cassandra
+ Compatible with C*’s CQL, SSTables, drivers, etc.
+ Written in C++ (not Java) on the Seastar framework
+ Shard-per-core design
+ “Async everywhere”
+ Shared-nothing
+ Futures/promises
+ Now also offers a DynamoDB-compatible API, Alternator
What is ScyllaDB?
Learn more: https://www.scylladb.com/product/technology/

6. 6
“Chasing Cassandra”
+ Scylla traditionally trailed implementation of Cassandra
+ Playing “catch-up” c. 2016 – 2020
+ Scylla 4.0 went beyond “feature completeness” for Cassandra 3.11
+ Now Scylla has features not found in Cassandra
+ Though Cassandra 4.0 has some features not (yet) present in Scylla
+ Some we’ll add for parity/compatibility
+ Some we’ll go our own way (solve differently, improve or obviate)

7. 7
Scylla Beyond Cassandra
Cassandra
“core”
Scylla same-
same
“core” iteration
Unique to
Cassandra
Unique to
Scylla
Scylla specific
implementation
Cassandra
specific
implementation
Same/similar feature implemented differently
May or may not be intercompatible
Same/similar feature implemented
identically/intercompatible
Not in Cassandra
Not in Scylla

8. 8
Comparing Open Source
Releases
Apache Cassandra vs. ScyllaDB

9. 9
+ February 2017: Cassandra 3.11 released
+ May 2019: First Roadmap for Cassandra 4.0 laid out
+ September 2019: First 4.0 Alpha
+ July 2020: First 4.0 Beta
+ April 26, 2021: Cassandra 4.0rc1
+ April 28, 2021: Cassandra 4.0 “World Party”
+ July 27, 2021: Actual Cassandra 4.0 Release Date
+ Sep, 07, 2021: Cassandra 4.0.1
+ >4 Years from last minor release (3.11) to 4.0
Cassandra 4.0 is Finally Here!

10. 10
Scylla’s Predictable Releases
Aug 2021: Apache Cassandra 4.0 vs. Scylla 4.4: Comparing Performance

11. 11
Scylla Open Source + Enterprise

12. 12
Head-to-Head
+ Scylla engineers make
~5x more commits/month
+ Bigger engineering team —
~50% more active committers
+ More active release cycle —
13x more major/minor releases
over past 3 years
+ More popular with developers —
Scylla exceeds Cassandra
in Github stars

13. 13
Comparing Public
Perception
Apache Cassandra vs. ScyllaDB

14. 14
Scylla Moving Up in the [DB-Engines.com] Rankings
ScyllaDB was 4th fastest rising database in
the DB-Engines.com Top 100 from Jan
2021 to Jan 2022 [Rank #85, Score 3.91]
Source: https://db-engines.com/en/ranking
Cassandra remains #11 overall in the
DB-Engines.com ranks for Jan 2022
[Score 123.55]

15. 15
Cassandra 4.0’s effect on DB-Engines.com
Cassandra 4.0 definitely boosted flagging popularity

16. 16
What’s the Same Between
Scylla & Cassandra?
Commonalities

17. 17
Common Ancestry
+ Cassandra and Scylla both
descend from the same historical
antecedents / whitepapers
+ Google’s Bigtable
+ Amazon’s Dynamo
+ Facebook’s Cassandra
+ [Not to be confused with
commercial offerings Google
Cloud Bigtable and Amazon
DynamoDB, or open source
Apache Cassandra]

18. 18
+ Peer-to-peer leaderless topology
+ Replication Factor (RF)
+ Tunable consistency per request
+ Multi datacenter replication
+ CAP Theorem: Availability/Partition
Tolerant “AP”
High Availability ᐩ No primary/replica complications
ᐩ Homogeneity of nodes
ᐩ Full datacenter loss can be survivable

19. 19
Ring Architecture
+ Token ring topology
+ Wide column “Key-key value”
+ Partition key
+ Clustering key
+ Nodes/vNodes
+ Automatic sharding
+ Same murmur3 partitioner &
hash algorithms

20. 20
Keyspaces, Tables
+ CREATE KEYSPACE
+ CREATE TABLE
+ ALTER KEYSPACE
+ ALTER TABLE
+ DROP KEYSPACE
+ DROP TABLE
ᐩ Pretty much standard Cassandra
Query Language (CQL)

21. 21
Basic CQL CRUD
Operations
+ Create [INSERT]
+ Read [SELECT]
+ Update [UPDATE]
+ Delete [DELETE]
+ WHERE clause
+ ALLOW FILTERING
+ TTL functions
ᐩ Pretty much standard Cassandra
Query Language (CQL)
ᐩ Like SQL, at least at cursory
glance, but do not be lulled into a
false sense of familiarity

22. 22
CQL Drivers
+ ScyllaDB can use all the
same Apache Cassandra and
DataStax drivers
+ Allows for a replacement of
ScyllaDB on the back end
without touching any existing
client apps or drivers
ᐩ They will not take advantage of
ScyllaDB’s shard-aware
architecture, but they’ll work

23. 23
+ <1 terabyte
+ 1 to 50 terabytes
+ 50-100 terabytes
+ >100 terabytes
How much data do you have under management in your own
transactional database systems?
Poll Question

24. 24
What’s similar but not
the same?
Cassandra and Scylla differences

25. 25
CQL
+ For the most part, all basic
CQL queries for Cassandra
will work with Scylla
+ Scylla uses the same CQL
wire protocol as Cassandra
ᐩ Scylla does implement some
features differently (we’ll get into
those)
ᐩ Naturally, those differences will
have related CQL commands
ᐩ Implementation lag:
Scylla is compatible to CQL 3.4.0;
current Cassandra CQL is 3.4.5

26. 26
SSTables
+ Scylla supports the same
immutable on-disk SSTable
LSM tree file formats
+ Standard compaction
algorithms are the same
(LCS, STCS, TWCS)
ᐩ Cassandra 4.0 implemented a new
“nb” SSTable file format
ᐩ Scylla will add support for “nb” file
format #8593
// na (4.0-rc1): uncompressed chunks,
pending repair session, isTransient,
checksummed sstable metadata file, new
Bloomfilter format
// nb (4.0.0): originating host id
ᐩ Scylla will also add support for “me”
file format #9869

27. 27
Lightweight
Transactions (LWT)
+ Both use Paxos consensus
algorithm
+ Compare-and-set operations
+ Also called “conditional updates”
ᐩ Scylla can accomplish LWTs in only
3 round trips (Cassandra takes 4)
ᐩ Scylla is more performant / efficient
ᐩ Blog:
https://www.scylladb.com/2020/07/15/
getting-the-most-out-of-lightweight-
transactions-in-scylla/
Scylla accomplishes LWTs in 3x round trips
Cassandra LWTs take 4x round trips

28. 28
Materialized Views
+ Cassandra: introduced in 3.0
[2017], but still experimental
+ Problems when base table gets
out of sync
+ To this day, major issues like
CASSANDRA-10346 are still open
ᐩ Scylla: production ready since 3.0 [Jan
2019]
ᐩ Serve as the infrastructural basis for
Secondary Indexes
ᐩ Can still get out of sync, but not easily
ᐩ Continually improving implementation
* Read more:
https://www.scylladb.com/2018/09/19/overheard-at-
distributed-data-summit/
“If you have them, take them out.”
— Nate McCall PMC Chair,
on Materialized Views in Cassandra [2018]*

29. 29
Secondary Indexes
+ Cassandra: only local Secondary
Indexes (SIs)
+ Scylla: both local and global SIs
+ The choice is now yours!
ᐩ https://www.scylladb.com/2019/07/23/
global-or-localsecondary-indexes-in-
scylla-the-choice-is-now-yours/
A global indexing query workflow in Scylla

30. 30
+ Introduced in C* 3.8, uses commitlog-like structure
+ Creates indexes as commit logs are written - for
improved performance and reliability
+ Feature enabled through cassandra.yaml
+ CDC can be enabled per table through ALTER TABLE
command
+ Currently, no standard way to read CDC files
+ DS planning to open source Kafka Source
connector
+ Advance replication from DS Labs
+ Example CDC project build by someone
Change Data
Capture (CDC)
CDC in Scylla
ᐩ Implemented as standard CQL Tables
ᐩ Just like adding another table
ᐩ Enabled by default
ᐩ Easy to integrate & consume
+ Deltas (changes) plus pre/post image
+ Replicated in same way as normal data
ᐩ Reasonable overhead
ᐩ TTL prevents unbounded data
ᐩ Easily consumable by Apache Kafka

31. 31
+ Debezium-based
+ Simply consumes CDC data via CQL
+ Doesn’t need to de-dupe data
+ Pumps data into Kafka topics
+ Confluent-certified
+ Less muss & fuss
Kafka CDC Source
Connector

32. 32
Zero Copy Streaming
vs. Row-level Repair
+ Cassandra now can stream
SSTables as a whole
+ Bypasses turning SStables into
objects (aka “object reification”)
providing 5x better performance
ᐩ Scylla implemented a completely
different approach in 2019
ᐩ Scylla’s row-level repair feature is
used instead of streaming
ᐩ Row-level repair is more:
○ Robust: Better able to endure
interruptions and outages
○ Granular: Only specific rows are
transferred
○ Efficient: There’s no extra data
streaming!

33. 33
+ C* 4.0 integrates async-driven code from
Netty library for communication between
nodes to leverage Java’s Non-Blocking IO
(NIO) capability.
+ A single thread pool for all connections to
corresponding nodes instead of
maintaining N threads per peer.
+ Potentially improves internode
performance issues, providing better tail
latencies and facilitating zero-copy
streaming.
Netty Async
Messaging
ᐩ Scylla also believes in non-blocking IO
ᐩ Scylla uses asynchronous / non blocking I/O
in C++ (aio) with its own schedulers
ᐩ Scylla per-core shards maintain as great a
shared-nothing approach as possible; use
async messaging when needed
ᐩ Read:
https://www.scylladb.com/2021/09/15/what-
weve-learned-after-6-years-of-io-scheduling/

34. 34
+ Plethora of K8s operators
+ DataStax K8ssandra 1.3+
+ Orange KassCop 2.0+
+ Bitnami Charts
+ [cass-operator deprecated]
+ Sidecars collocated/run on the same
instance as the DB server daemon
+ What Works and What Doesn’t:
https://k8ssandra.io/blog/articles/ku
bernetes-and-apache-cassandra-
what-works-and-what-doesnt/
Kubernetes Support
& Sidecars
ᐩ Scylla Operator offers great K8s
support — It just works
ᐩ Scylla Manager Agent is a sidecar
and already included by default with
Scylla Operator
ᐩ https://www.scylladb.com/product/
scylla-operator-kubernetes/

35. 35
What’s Just Totally
Different?
Cassandra and Scylla differences

36. 36
Shard-per-Core
Architecture
+ Based Seastar framework
(also used in Redpanda,
Redhat Crimson)
+ Designed/optimized for
multicore systems (scales to
100+ CPUs per node)
ᐩ Cassandra is shard-per-node
ᐩ Scylla balances data with more
granularity

37. 37
Shard-Aware Drivers ᐩ Our shard-aware Rust driver serves as
the paradigm for our new shard-aware
drivers
ᐩ Still backwards-compatible with
Cassandra
ᐩ Get it on Github!
https://github.com/scylladb/scylla-rust-driver
+ Better performance than a
“vanilla” CQL driver
+ “Smart” token-aware clients
direct queries to specific shards
(cores) where data resides
+ Better for consumption of CDC
data tables
+ Up to 25% greater performance

38. 38
+ Gossip in Cassandra requires seed
nodes; which violates the idea of
homogeneity of nodes
+ Requires manual assignment and
configuration
+ Seed nodes do not bootstrap
+ Complicated to add new seed node
or replace a dead seed node
Seedless Gossip ᐩ Scylla implemented gossip without
requiring seed nodes
ᐩ More symmetric; less problematic
ᐩ Read more:
https://www.scylladb.com/2020/09/22/s
eedless-nosql-getting-rid-of-seed-nodes-
in-scylla/

39. 39
+ Run your DynamoDB-compatible
workloads anywhere:
+ on AWS or in an AWS Outpost
+ on Google Cloud, Azure, or
+ on-premises
+ Supports DynamoDB Streams
+ Supports Load Balancing
+ Scylla Spark Migrator to move data
to any Scylla cluster anywhere
DynamoDB-compatible
API (Alternator)
ᐩ Cassandra has no comparable feature

40. 40
+ Schema Changes
+ Topology Changes
+ Add or remove any number of
nodes simultaneously
+ Durable and linearizable
+ Background Data Rebalancing
+ Tablets!
+ Immediate, Strong Consistency
of MVs, SIs, CDC tables
+ 1 Round Trip!
Raft in ScyllaDB
Not in Cassandra

41. 41
Benchmarking:
Cassandra 4.0 vs Scylla 4.4
and how Scylla dominates

42. 42
Cassandra 4.0 vs. Scylla 4.4
+ Scylla up to 100x lower P99 latencies
+ Scylla can maintain 2x - 5x throughput
+ Scylla adds nodes 3x faster

43. 43
Scylla 4.4 vs. Cassandra 4.0
+ Cassandra 4.0 cannot
maintain useable
low latencies except
at very low throughput
(≤30-40k ops)
+ Scylla can maintain
low latencies for far
greater throughputs
(≤170-180k ops)

44. 44
Replacing a Node
+ Scylla can heal clusters far
faster than Cassandra 4.0 by
spinning nodes up and
rebalancing data
~3x - 4x faster

45. 45
Doubling Cluster Capacity
+ Scylla doubled a cluster’s
capacity in just over
an hour and a half
(94 minutes)
+ It took Cassandra 4.0
just shy of 4 hours
(238 minutes)
to perform the same task
+ Scylla performed 2.5X faster

46. 46
+ Scylla 4.4: 36 min on a 3-node cluster
+ Cassandra 4.0 took 36x - 63x as long
(nearly a day; or a day and a half!)
+ Cassandra 4.0 performed worse than
Cassandra 3.11 with num_tokens: 16
Major Compaction Speed

47. 47
TCO Comparison: 4 vs. 40
+ 4x i3.metal instances with Scylla
provided the same or better performance
as 40 nodes of Cassandra on i3.4xlarge
+ Cassandra had 640 vCPUs
+ Scylla had 288 vCPUs
+ Scylla got better utility out of hardware
+ Cost savings of 60%
+ Administrative burden/attack surface
reduced by 90%

48. 48
BLOGS
+ Benchmark, Part 1: Cassandra 4.0 vs. Cassandra 3.11: Comparing Performance
+ Benchmark, Part 2: Apache Cassandra 4.0 vs. Scylla 4.4: Comparing Performance
+ Webinar: Your Questions about Cassandra 4.0 vs. Scylla 4.4 Answered
WEBINAR
+ Comparing Apache Cassandra 4.0, 3.0 and ScyllaDB
Published Benchmarks

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