Software Crafters

Meet-up₂₂

Architecture Kata

Let's Introduce ourselves

• Name
• Where you work/study

What would you do, if you bumped your car into someone’s else and there was nobody around?

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Timeline

2.00 - 3.00: Kick-off & discussion

3.00 - 4.00: Architecture Kata in mobs

4.00 - 4.50: Groups present their solutions

4.50 - 5.00: Retrospective

Consider Ambulance as a Service

1. Ambulance can be requested from a mobile device
2. Ambulance’s location can be traced in real time.
3. Ambulance can see areas most affected by Covid
4. Ambulance where about for a day can be plotted on map

MySQL

Database

Ambulance Web Server

Problem?

If one ambulance sends location once in 3 seconds

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Pings in minute = 20

If 1000 Ambulance sends location once in 3 seconds

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Pings in minute = 20,000

Pings in second = 333.33

One Ambulance

Message Queues

1. A highly available service (messages are never lost)
2. Producer can push messages
3. Consumers poll message queue and process the messages
4. Consumer consumes message at its own pace

Ambulance Web Server

Problem?

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SELECT geo_hash(pickup_latitude, pickup_longitude), COUNT(1)

FROM ambulance_requests ar

JOIN patient p ON ar.patient_id = p.id

WHERE p.disease = 'Covid-19'

AND ar.date > date_sub(NOW(), INTERVAL 30 DAY)

GROUP BY 1;

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10 Cases in a week vs 10 Cases in an hour

100 Rows vs 10000 Rows

Caches

1. Calculate results once and store them for
1. Faster retrieval
2. Avoiding expensive operation running again and again
2. Runs at O(1)
3. Is basically a key/value pair

When to cache? (examples)

1. Expensive database query
2. Expensive computation
3. Expensive http call
4. The result is predetermined based on arguments

Problem?

If 1000 Ambulance sends location once in 3 seconds

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Pings in second = 333.33

Pings in minute = 20000

Pings in day = 28,800,000

Pings in month = 864,000,000

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SQL

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• Good for running aggregations
• Good for transactions
• Only vertically scalable
• Any column can be queried efficiently with help of index

NoSQL

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• Good for parent/child hierarchy
• Horizontally scalable
• Can only be queried with primary key

Let’s create something

Scalable Chat Application

• Must
• Should be able to handle 100k messages being sent per hour
• Should receive message instantly
• Should be able to retrieve a specific conversation within one second
• Should be able to create groups and have group conversations
• Should be able to delete recent messages from receiver’s end
• Good to Have
• Should be able to reply to a specific message
• Should be able to have threads
• Should be able to understand the demographics of users (active users in Karachi at 10pm)

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BreakoutRooms

BreakoutRooms

BreakoutRooms

RETRO

Everyone discusses their solution

Discussion on what Kata is about

4.00 pm

3.00 pm