API Design Patterns

API Design Patterns draws on the collected wisdom of the API community, including the internal developer knowledge base at Google, laying out an innovative set of design patterns for developing both internal and public-facing APIs. In this essential guide, Google Software Engineer JJ Geewax provides a unique and authoritative catalog of patterns that promote flexibility and eas...

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API Design Patterns draws on the collected wisdom of the API community, including the internal developer knowledge base at Google, laying out an innovative set of design patterns for developing both internal and public-facing APIs. In this essential guide, Google Software Engineer JJ Geewax provides a unique and authoritative catalog of patterns that promote flexibility and ease-of-use in your APIs. Each pattern in the catalog is fully illustrated with its own example API, use-cases for solving common API design challenges, and scenarios for tricky edge issues using a pattern’s more subtle features. With the best practices laid out in this book, you can ensure your APIs are adaptive in the face of change and easy for your clients to incorporate into their projects.

what's inside

A full case-study of building an API and adding features

The guiding principles that underpin most API patterns

Fundamental patterns for resource layout and naming

Advanced patterns for special interactions and data transformations

Part 1: Introduction
1 Introduction to APIs
1.1 What are web APIs?
1.2 Why do APIs matter?
1.3 What are resource-oriented APIs?
1.4 What makes an API “good”?
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Part 1: Introduction
1 Introduction to APIs
1.1 What are web APIs?
1.2 Why do APIs matter?
1.3 What are resource-oriented APIs?
1.4 What makes an API “good”?
1.4.1 Operational
1.4.2 Expressive
1.4.3 Simple
1.4.4 Predictable
2 Introduction to API design patterns
2.1 What are API design patterns?
2.2 Why are API design patterns important?
2.3 Anatomy of an API design pattern
2.3.1 Name and synopsis
2.3.2 Motivation
2.3.3 Overview
2.3.4 Implementation
2.3.5 Trade-offs
2.4 Case study: Twapi, a Twitter-like API
2.4.1 Overview
2.4.2 Listing messages
2.4.3 Exporting data
Part 2: Design principles
3 Naming
3.1 Why do names matter?
3.2 What makes a name “good”?
3.2.1 Expressive
3.2.2 Simple
3.2.3 Predictable
3.3 Language, grammar, and syntax
3.3.1 Language
3.3.2 Grammar
3.3.3 Syntax
3.4 Context
3.5 Data types and units
3.6 Case study: What happens when you choose bad names?
3.7 Exercises
4 Resource scope and hierarchy
4.1 What is resource layout?
4.1.1 Types of relationships
4.1.2 Entity relationship diagrams
4.2 Choosing the right relationship
4.2.1 Do you need a relationship at all?
4.2.2 References or in-line data
4.2.3 Hierarchy
4.3 Anti-patterns
4.3.1 Resources for everything
4.3.2 Deep hierarchies
4.3.3 In-line everything
4.4 Exercises
5 Data types and defaults
5.1 Introduction to data types
5.1.1 Missing vs. null
5.2 Booleans
5.3 Numbers
5.3.1 Bounds
5.3.2 Default values
5.3.3 Serialization
5.4 Strings
5.4.1 Bounds
5.4.2 Default values
5.4.3 Serialization
5.5 Enumerations
5.6 Lists
5.6.1 Atomicity
5.6.2 Bounds
5.6.3 Default values
5.7 Maps
5.7.1 Bounds
5.7.2 Default values
5.8 Exercises
Part 3: Fundamentals
6 Resource identification
6.1 What is an identifier?
6.2 What makes a good identifier?
6.2.1 Easy to use
6.2.2 Unique
6.2.3 Permanent
6.2.4 Fast and easy to generate
6.2.5 Unpredictable
6.2.6 Readable, shareable, and verifiable
6.2.7 Informationally dense
6.3 What does a good identifier look like?
6.3.1 Data type
6.3.2 Character set
6.3.3 Identifier format
6.3.4 Checksums
6.3.5 Resource type
6.3.6 Hierarchy and uniqueness scope
6.4 Implementation
6.4.1 Size
6.4.2 Generation
6.4.3 Tomb-stoning
6.4.4 Checksum
6.4.5 Database storage
6.5 What about UUIDs?
6.6 Exercises
7 Standard methods
7.1 Motivation
7.2 Overview
7.3 Implementation
7.3.1 Which methods should be supported?
7.3.2 Idempotence and side effects
7.3.3 Get
7.3.4 List
7.3.5 Create
7.3.6 Update
7.3.7 Delete
7.3.8 Replace
7.3.9 Final API definition
7.4 Trade-offs
7.5 Exercises
8 Partial updates and retrievals
8.1 Motivation
8.1.1 Partial retrieval
8.1.2 Partial update
8.2 Overview
8.3 Implementation
8.3.1 Transport
8.3.2 Maps and nested interfaces
8.3.3 Repeated fields
8.3.4 Default values
8.3.5 Implicit field masks
8.3.6 Updating dynamic data structures
8.3.7 Invalid fields
8.3.8 Final API definition
8.4 Trade-offs
8.4.1 Universal support
8.4.2 Alternative implementations
8.5 Exercises
9 Custom methods
9.1 Motivation
9.1.1 Why not just standard methods?
9.2 Overview
9.3 Implementation
9.3.1 Side effects
9.3.2 Resources vs. collections
9.3.3 Stateless custom methods
9.3.4 Final API definition
9.4 Trade-offs
9.5 Exercises
10 Long-running operations
10.1 Motivation
10.2 Overview
10.3 Implementation
10.3.1 What does an LRO look like?
10.3.2 Resource hierarchy
10.3.3 Resolution
10.3.4 Error handling
10.3.5 Monitoring progress
10.3.6 Canceling operations
10.3.7 Pausing and resuming operations
10.3.8 Exploring operations
10.3.9 Persistence
10.3.10 Final API definition
10.4 Trade-offs
10.5 Exercises
11 Rerunnable jobs
11.1 Motivation
11.2 Overview
11.3 Implementation
11.3.1 Job resources
11.3.2 The custom run method
11.3.3 Job execution resources
11.3.4 Final API definition
11.4 Trade-offs
11.5 Exercises
Part 4: Resource relationships
12 Singleton sub-resources
12.1 Motivation
12.1.1 Why should we use a singleton sub-resource?
12.2 Overview
12.3 Implementation
12.3.1 Standard methods
12.3.2 Resetting
12.3.3 Hierarchy
12.3.4 Final API definition
12.4 Trade-offs
12.4.1 Atomicity
12.4.2 Exactly one sub-resource
12.5 Exercises
13 Cross references
13.1 Motivation
13.2 Overview
13.3 Implementation
13.3.1 Reference field name
13.3.2 Data integrity
13.3.3 Value vs. reference
13.3.4 Final API definition
13.4 Trade-offs
11.5 Exercises
14 Association resources
14.1 Motivation
14.2 Overview
14.2.1 Association alias methods
14.3 Implementation
14.3.1 Naming the association resource
14.3.2 Standard method behavior
14.3.3 Uniqueness
14.3.4 Read-only fields
14.3.5 Association alias methods
14.3.6 Referential integrity
14.3.7 Final API definition
14.4 Trade-offs
14.4.1 Complexity
14.4.2 Separation of associations
14.5 Exercises
15 Add and remove custom methods
15.1 Motivation
15.2 Overview
15.3 Implementation
15.3.1 Listing associated resources
15.3.2 Data integrity
15.3.3 Final API definition
15.4 Trade-offs
15.4.1 Nonreciprocal relationship
15.4.2 Relationship metadata
15.5 Exercises
16 Polymorphism
16.1 Motivation
16.2 Overview
16.3 Implementation
16.3.1 Deciding when to use polymorphic resources
16.3.2 Polymorphic structure
16.3.3 Polymorphic behavior
16.3.4 Why not polymorphic methods?
16.3.5 Final API definition
16.4 Trade-offs
16.5 Exercises
Part 5: Collective operations
17 Copy and move
17.1 Motivation
17.2 Overview
17.3 Implementation
17.3.1 Identifiers
17.3.2 Child resources
17.3.3 Related resources
17.3.4 External data
17.3.5 Inherited metadata
17.3.6 Atomicity
17.3.7 Final API definition
17.4 Trade-offs
17.5 Exercises
18 Batch operations
18.1 Motivation
18.2 Overview
18.3 Implementation
18.3.1 Atomicity
18.3.2 Operation on the collection
18.3.3 Ordering of results
18.3.4 Common fields
18.3.5 Operating across parents
18.3.6 Batch Get
18.3.7 Batch Delete
18.3.8 Batch Create
18.3.9 Batch Update
18.3.10 Final API definition
18.4 Trade-offs
18.5 Exercises
19 Criteria-based deletion
19.1 Motivation
19.2 Overview
19.3 Implementation
19.3.1 Filtering results
19.3.2 Validation only by default
19.3.3 Result count
19.3.4 Result sample set
19.3.5 Consistency
19.3.6 Final API definition
19.4 Trade-offs
19.5 Exercises
20 Anonymous writes
20.1 Motivation
20.2 Overview
20.3 Implementation
20.3.1 Consistency
20.3.2 Final API definition
20.4 Trade-offs
20.5 Exercises
21 Pagination
21.1 Motivation
21.2 Overview
21.3 Implementation
21.3.1 Page size
21.3.2 Page tokens
21.3.3 Total count
21.3.4 Paging inside resources
21.3.5 Final API definition
21.4 Trade-offs
21.4.1 Bi-directional paging
21.4.2 Arbitrary windows
21.5 Anti-pattern: Offsets and limits
21.6 Exercises
22 Filtering
22.1 Motivation
22.2 Overview
22.3 Implementation
22.3.1 Structure
22.3.2 Filter syntax and behavior
22.3.3 Final API definition
22.4 Trade-offs
22.5 Exercises
23 Importing and exporting
23.1 Motivation
23.2 Overview
23.3 Implementation
23.3.1 Import and export methods
23.3.2 Interacting with storage systems
23.3.3 Converting between resources and bytes
23.3.4 Consistency
23.3.5 Identifiers and collisions
23.3.6 Handling related resources
23.3.7 Failures and retries
23.3.8 Filtering and field masks
23.3.9 Final API definition
23.4 Trade-offs
23.5 Exercises
Part 6: Safety and security
24 Versioning and compatibility
24.1 Motivation
24.2 Overview
24.2.1 What is compatibility?
24.2.2 Defining backward compatibility
24.3 Implementation
24.3.1 Perpetual stability
24.3.2 Agile instability
24.3.3 Semantic versioning
24.4 Trade-offs
24.4.1 Granularity vs. simplicity
24.4.2 Stability vs. new functionality
24.4.3 Happiness vs. ubiquity
24.5 Exercises
25 Soft deletion
25.1 Motivation
25.2 Overview
25.3 Implementation
25.3.1 Deleted designation
25.3.2 Modifying standard methods
25.3.3 Undeleting
25.3.4 Expunging
25.3.5 Expiration
25.3.6 Referential integrity
25.3.7 Effects on other methods
25.3.8 Adding soft delete across versions
25.3.9 Final API definition
25.4 Trade-offs
25.5 Exercises
26 Request deduplication
26.1 Motivation
26.2 Overview
26.3 Implementation
26.3.1 Request identifier
26.3.2 Response caching
26.3.3 Consistency
26.3.4 Request ID collisions
26.3.5 Cache expiration
26.3.6 Final API definition
26.4 Trade-offs
26.5 Exercises
27 Request validation
27.1 Motivation
27.2 Overview
27.3 Implementation
27.3.1 External dependencies
27.3.2 Special side effects
27.3.3 Final API definition
27.4 Trade-offs
27.5 Exercises
28 Resource revisions
28.1 Motivation
28.2 Overview
28.3 Implementation
28.3.1 Revision identifiers
28.3.2 Creating revisions
28.3.3 Retrieving specific revisions
28.3.4 Listing revisions
28.3.5 Restoring a previous revision
28.3.6 Deleting revisions
28.3.7 Handling child resources
28.3.8 Final API definition
28.4 Trade-offs
28.5 Exercises
29 Request retrial
29.1 Motivation
29.2 Overview
29.2.1 Client-side retry timing
29.2.2 Server-specified retry timing
29.3 Implementation
29.3.1 Retry eligibility
29.3.2 Exponential back-off
29.3.3 Retry After
29.3.4 Final API definition
29.4 Trade-offs
29.5 Exercises
30 Request authentication
30.1 Motivation
30.1.1 Origin
30.1.2 Integrity
30.1.3 Nonrepudiation
30.2 Overview
30.3 Implementation
30.3.1 Credential generation
30.3.2 Registration and credential exchange
30.3.3 Generating and verifying raw signatures
30.3.4 Request fingerprinting
30.3.5 Including the signature
30.3.6 Authenticating requests
30.3.7 Final API definition
30.4 Trade-offs
30.5 Exercises
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