Event schema design in Microservices - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a table for storing event data with an event ID as the primary key.

Microservices

CREATE TABLE events (event_id [1] PRIMARY KEY, event_name VARCHAR(100));

Drag options to blanks, or click blank then click option'

AINT

BVARCHAR(50)

CDATE

DTEXT

Attempts:

3 left

💡 Hint

Common Mistakes

Using VARCHAR for event_id which is less efficient for keys.

Using DATE type which is not suitable for IDs.

The event_id should be an integer type to uniquely identify each event and serve as the primary key.

2fill in blank

medium

Complete the code to add a timestamp column to record when the event occurred.

Microservices

ALTER TABLE events ADD COLUMN event_time [1];

Drag options to blanks, or click blank then click option'

ATIMESTAMP

BINT

CVARCHAR(50)

DBOOLEAN

Attempts:

3 left

💡 Hint

Common Mistakes

Using INT which cannot store date/time.

Using BOOLEAN which is only true/false.

The TIMESTAMP type stores date and time information, perfect for recording event occurrence time.

3fill in blank

hard

Fix the error in the event schema by choosing the correct data type for event payload storage.

Microservices

CREATE TABLE event_payloads (payload_id INT PRIMARY KEY, event_id INT, payload [1]);

Drag options to blanks, or click blank then click option'

AINT

BTEXT

CVARCHAR(255)

DBOOLEAN

Attempts:

3 left

💡 Hint

Common Mistakes

Using VARCHAR(255) which may be too short for large payloads.

Using INT or BOOLEAN which cannot store text.

Event payloads can be large JSON or text data, so TEXT type is suitable for flexible storage.

4fill in blank

hard

Fill both blanks to create a foreign key relationship between event_payloads and events tables.

Microservices

ALTER TABLE event_payloads ADD CONSTRAINT fk_event FOREIGN KEY ([1]) REFERENCES [2](event_id);

Drag options to blanks, or click blank then click option'

Aevent_id

Bevents

Cpayload_id

Devent_payloads

Attempts:

3 left

💡 Hint

Common Mistakes

Using payload_id as foreign key which is incorrect.

Referencing the wrong table.

The foreign key column is event_id in event_payloads, referencing event_id in events table.

5fill in blank

hard

Fill all three blanks to create an index on event_time and event_name for faster queries.

Microservices

CREATE INDEX idx_[1] ON events ([2], [3]);

Drag options to blanks, or click blank then click option'

Atime_name

Bevent_time

Cevent_name

Devent_id

Attempts:

3 left

💡 Hint

Common Mistakes

Using event_id in the index which is already primary key.

Choosing a non-descriptive index name.

The index name is arbitrary but descriptive. Indexing event_time and event_name speeds up queries filtering or sorting by these columns.

Practice

1. What is the main purpose of an event schema in microservices?

easy

A. To define the structure and content of messages exchanged between services

B. To store user data in a database

C. To create user interfaces for microservices

D. To manage network connections between services

Solution

1. Step 1: Understand event schema role

   An event schema defines how messages look when services talk to each other.

2. Step 2: Identify correct purpose

   It ensures all services understand the message format and data.

3. Final Answer:

   To define the structure and content of messages exchanged between services -> Option A

4. Quick Check:

   Event schema = message format [OK]

Hint: Event schema = message format for services [OK]

Common Mistakes:

• Confusing event schema with database storage
• Thinking event schema manages UI or network
• Assuming event schema is about service deployment

2. Which of the following is a correct JSON snippet for an event schema with type and timestamp?

easy

A. {eventType: "OrderCreated", "timestamp": "2024-06-01T12:00:00Z"}

B. {"eventType": OrderCreated, "timestamp": 2024-06-01T12:00:00Z}

C. {"eventType": "OrderCreated", timestamp: "2024-06-01T12:00:00Z"}

D. {"eventType": "OrderCreated", "timestamp": "2024-06-01T12:00:00Z"}

Solution

1. Step 1: Check JSON syntax rules

   Keys and string values must be in double quotes; commas separate pairs.

2. Step 2: Validate each option

   {"eventType": "OrderCreated", "timestamp": "2024-06-01T12:00:00Z"} uses correct quotes and format; others miss quotes or have invalid syntax.

3. Final Answer:

   {"eventType": "OrderCreated", "timestamp": "2024-06-01T12:00:00Z"} -> Option D

4. Quick Check:

   Valid JSON = {"eventType": "OrderCreated", "timestamp": "2024-06-01T12:00:00Z"} [OK]

Hint: JSON keys and strings need double quotes [OK]

Common Mistakes:

• Missing quotes around keys or string values
• Using unquoted date/time strings
• Omitting commas between pairs

3. Given this event schema snippet:

{"eventType": "UserSignedUp", "timestamp": "2024-06-01T10:00:00Z", "data": {"userId": 123, "email": "[e-mail]"}}

What will be the value of data.email in the event?

medium

A. 123

B. "UserSignedUp"

C. "[e-mail]"

D. 2024-06-01T10:00:00Z

Solution

1. Step 1: Locate the data field in the event

   The event has a nested object under "data" with keys "userId" and "email".

2. Step 2: Identify the value of data.email

   The value for "email" is "[e-mail]" as a string.

3. Final Answer:

   "[e-mail]" -> Option C

4. Quick Check:

   data.email = "[e-mail]" [OK]

Hint: Look inside data object for email key [OK]

Common Mistakes:

• Confusing userId with email
• Picking eventType or timestamp instead
• Ignoring nested structure

4. Identify the error in this event schema:

{"eventType": "PaymentProcessed", "timestamp": "2024-06-01T15:00:00Z", "data": {"amount": 100, "currency": USD}}

medium

A. Missing comma after amount key

B. Missing quotes around the currency value USD

C. timestamp format is incorrect

D. eventType should be lowercase

Solution

1. Step 1: Check JSON value types

   String values must be in double quotes; USD is unquoted here.

2. Step 2: Verify other parts

   Comma after amount is present, timestamp format is ISO standard, eventType case is allowed.

3. Final Answer:

   Missing quotes around the currency value USD -> Option B

4. Quick Check:

   Strings need quotes [OK]

Hint: String values must have quotes in JSON [OK]

Common Mistakes:

• Ignoring missing quotes on string values
• Thinking timestamp format is wrong
• Assuming key case matters in JSON

5. You want to design an event schema for a microservice that sends user profile updates. Which design choice improves schema flexibility for future changes?

hard

A. Include a 'metadata' field to hold optional extra info

B. Fix the schema to only allow 'name' and 'email' fields

C. Use a flat schema without nested objects

D. Exclude timestamps to reduce message size

Solution

1. Step 1: Understand schema flexibility needs

   Flexible schemas allow adding new info without breaking existing services.

2. Step 2: Evaluate options for flexibility

   Adding a 'metadata' field lets you add optional data later safely.

3. Final Answer:

   Include a 'metadata' field to hold optional extra info -> Option A

4. Quick Check:

   Optional metadata = flexible schema [OK]

Hint: Add metadata field for optional future data [OK]

Common Mistakes:

• Fixing schema too rigidly limits future changes
• Removing timestamps loses event timing info
• Avoiding nested objects reduces clarity