This document discusses different API options for databases: REST, gRPC, and GraphQL. It begins with an overview of Apache Cassandra and its key features as a distributed database. It then covers an API design methodology, including conceptual and logical data modeling, mapping queries to tables, and creating the physical schema. The document presents criteria for evaluating API choices and provides pros and cons of REST, gRPC, and GraphQL. It concludes that REST is best for CRUD operations, gRPC for high performance services, and GraphQL for discoverability and flexible payloads.

1. Designing API for
Databases:
‪ Which one should you pick ?
GraphQL
@clunven | #voxxed_lu | @voxxed_lu
Casino 2000, Luxembourg

2. @clunven | @voxxed_lu | #voxxed_lu
About me
Cedrick Lunven
Developer Advocate
Creator Contributor

3. © DataStax, All Rights Reserved.Confidential © DataStax, All Rights Reserved.
Agenda 2
3
4 DECISION TREE
DEMONSTRATION AND CODE REVIEW
API DESIGN METHODOLOGY
1 APACHE CASSANDRA™ OVERVIEW

4. APACHE CASSANDRA™
Quick Overview

5. @clunven | @voxxed_lu | #voxxed_lu
This is a DISTRIBUTED Database
Node
• Up to 1TB
• 3000 Tx/s/core

6. @clunven | @voxxed_lu | #voxxed_lu
…which scale linearly

7. @clunven | @voxxed_lu | #voxxed_lu
Data is distributed
0
13
25
38
50
63
75
88 59 (data)
RF=2
59 (data)
RF=3
replicated

8. @clunven | @voxxed_lu | #voxxed_lu
Cassandra is « AP »
Consistency
Partition
Tolerance
Availability

9. @clunven | @voxxed_lu | #voxxed_lu
Tuneable Consistency
RF=3
Client CL=ONECL=QUORUMCL=ALL

10. @clunven | @voxxed_lu | #voxxed_lu
…anywhere
Cluster
Datacenter (Ring)

11. @clunven | @voxxed_lu | #voxxed_lu
Sweet spots
1. High Throughput (because we can keep up)
2. High Volume (because we scale linearly and still OLTP)
3. High Availability (replication, masterless)
4. Data distribution (read/write around the globe)

12. @clunven | @voxxed_lu | #voxxed_lu
• Le KEYSPACE est comme un schéma
dans Oracle, une isolation des
données
12
Projet_X Keyspace
Une table contient une CLEF
PRIMAIRE contenant 2 parties : La
partition key et le reste (clustering
columns). Chaque valeur de
partition key est hashée sous la
forme d’un token.
Plusieurs lignes avec la même
partition key constitue une
partition.
Data Modelling

13. @clunven | @voxxed_lu | #voxxed_lu
• Syntaxe proche du SQL pour
les bases relationnelles
• Création des objets avec le
DDL :
• CREATE, INSERT, UPDATE,
DELETE, GRANT, REVOKE,
SELECT, WHERE
13
Exemple
CREATE TABLE market_prices (
symbol TEXT,
date TIMESTAMP,
price DECIMAL,
side INT,
PRIMARY KEY (symbol, date)
) WITH CLUSTERING ORDER BY(date DESC);
Cassandra Query Language

14. LIST, SET, MAP, UDT

15. API DESIGN METHODOLOGY
From zero to hero

16. @clunven | @voxxed_lu | #voxxed_lu
Reference Application
http://killrvideo.github.io

17. @clunven | @voxxed_lu | #voxxed_lu
Api Design Methodology
1
killrvideo-dse
Drivers
DAO3
killrvideo-api-rest killrvideo-api-grpc killrvideo-api-graphql
2

18. @clunven | @voxxed_lu | #voxxed_lu
Designing Data Model
Entities & Relationships
Queries

19. @clunven | @voxxed_lu | #voxxed_lu
Conceptual Data Model

20. @clunven | @voxxed_lu | #voxxed_lu
Application Workflow
R1: Find comments related to target video using its identifier
• Get most recent first
• Implement Paging
R2: Find comments related to target user using its identifier
• Get most recent first
• Implement Paging
R3: Implement CRUD operations

21. @clunven | @voxxed_lu | #voxxed_lu
Mapping
Q2: Find comments posted for a user with a
known id (show most recent first)
comments_by_video
comments_by_user
Q1: Find comments for a video with a
known id (show most recent first)
Q3: CRUD Operations

22. @clunven | @voxxed_lu | #voxxed_lu
Logical Data Model
userid
creationdate
commentid
videoid
comment
comments_by_user
K
C
↑
videoid
creationdate
commentid
userid
comment
comments_by_video
C
↑
K
C
↑
↑C

23. @clunven | @voxxed_lu | #voxxed_lu
Physical Data Model
userid
commentid
videoid
comment
comments_by_user
TIMEUUID
K
TEXT
C
UUID
UUID
↑
videoid
commentid
userid
comment
comments_by_video
TIMEUUID
K
TEXT
C
UUID
UUID
↑

24. @clunven | @voxxed_lu | #voxxed_lu
Schema DDL
CREATE TABLE IF NOT EXISTS comments_by_user (
userid uuid,
commentid timeuuid,
videoid uuid,
comment text,
PRIMARY KEY ((userid), commentid)
) WITH CLUSTERING ORDER BY (commentid DESC);
CREATE TABLE IF NOT EXISTS comments_by_video (
videoid uuid,
commentid timeuuid,
userid uuid,
comment text,
PRIMARY KEY ((videoid), commentid)
) WITH CLUSTERING ORDER BY (commentid DESC);

25. @clunven | @voxxed_lu | #voxxed_lu
How?
Conceptual Data
Model
(Entities, Relations)
Application Workflow
(Queries)
Database Family
(Technos +Table)

27. @clunven | @voxxed_lu | #voxxed_lu

28. @clunven | @voxxed_lu | #voxxed_lu

29. DECISION TREE
Because we are serious

30. @clunven | @voxxed_lu | #voxxed_lu
Analysis Criteria
📋 Conceptual
Data Model
Application
Workflow
(Queries)
Database Family
(Technos
+Table)
Caching
Syncvs AsyncReactive
SLA (Volume)
Data Integrity
Filters
Paging
Sort
Latencies Throughput
Versionning
Confidentiality
Atomicity
Cardinality
Developers
👤 Users/Consumers
Language
CodeFirst/
Vs SchemaFirst
Documentation
Test
Build
Packaging
Api Catalog
Internalvs
Public Techno
Profile
XP

31. @clunven | @voxxed_lu | #voxxed_lu
Analysis Matrix

32. @clunven | @voxxed_lu | #voxxed_lu
Decision Tree

33. @clunven | @voxxed_lu | #voxxed_lu
 Decoupling Client / Server (Schema on read)
 Flexibility: Sync, Async, Reactive + Multi payload
 Api Lifecycle (Versioning)
 Tooling (API Management, Serverless)
 Verbose payloads (json, xml)
 No discoverability
 Not best fit for command-like (functions) API (RPC)
 CRUD superstar
 Relevant for OLTP mutations and statuses
 Public and web APIs

34. @clunven | @voxxed_lu | #voxxed_lu
 High Performances (http/2 – binary serialisation)
 Multiple stubs : Sync, Async, Streaming
 Multi languages (Interoperability)
 Strongly coupled (schema with proto files)
 No discoverability
 Protobuf serialization format
 Distributed network of services (no waits)
 High throughput & streaming use cases
 Command-like, RPC

35. @clunven | @voxxed_lu | #voxxed_lu
 Discoverability, documentation
 Custom payloads
 Match standards (Json | Http)
 Single endpoint (versioning, monitoring, security)
 Complex implementation (tooling, still young)
 Nice for customers nasty for DB (N+1 select)
 BFF : Backend for frontend
 Service aggregation | composition (joins)
 When bandwidth matters (mobile phones)
GraphQL

36. RESOURCES
Because COPY/PASTE is the most important skill for developers

37. @clunven | @voxxed_lu | #voxxed_lu
References
https://github.com/clun/api_Rest_Grpc_GraphQL

38. THANK YOU