P.S: This was presented at the Software Architect's Bangalore meetup. So, this is not completely consumable on it's own. A war biopic on Migrating a multi-tenant app to Azure. This presentation is a combination of Learnings and Lessons in planning and executing migration of multi-tenant app to Azure (or in general to cloud).Talks about the original on-premise architecture, challenges faced in migration and the architecture after migrating to azure. https://www.meetup.com/SoftwareArchitectsBangalore/events/237117024/

1. Migrating Multi-tenant App to Azure
Akshay Surve,
CTO DeltaX
Twitter: @ak47suve
Email: akshay@deltax.com

2. About Me
● 10+ years
Shipping Ideas, Making Mistakes, GTD
Marathons / Hackathons / *-athon :)
● Co-founded DeltaX in 2013
Ad-tech / Product Startup / 30+ team
300+ advertisers across India, APAC and US.

3. What to Expect?
● Our journey to the Cloud
Migrating our 1.2TB+ DB 100 odd tenants, Application & Services from bare
metal dedicated infrastructure to the cloud
● Key Considerations & Pointers
● Learnings & Opinions

4. Context (What we do?)
● SAAS platform for advertising analytics and tracking.
● We had 2 parallel stacks
○ Auto-scaled HA ad-serving + tracking system - AWS
Node.js / Route53 > ELB > EC2 (auto-scale) > AWS S3 > Cloudfront
○ Always ON Mini-datawarehouse per tenant - Bare-metal Servers
This is the stack we migrated to Azure

5. Previous Setup (Infrastructure stack)
DB Machine
Dual Intel® Xeon®
E5-2600 v3 @ 2.10GHz octa-core incl.
RAM 128+23GB DDR4 ECC RAM
2 x 480 GB 6 Gb/s SSD Datacenter Edition
6 x 960 GB 6 Gb/s SSD Datacenter Edition
1 x 32 GB DDR4 Reg. ECC RAM
Web Box
Single Intel® Xeon®
E5-2600 v3 @ 2.10GHz octa-core incl.
64 GB DDR4 ECC RAM
Services Box
Single Intel® Xeon®
E5-2600 v3 @ 2.10GHz octa-core incl.
64 GB DDR4 ECC RAM

6. Bottlenecks
● Tenant Isolation
Small vs Big tenants; Access to their own data;
● Dev Ops / Managing Infrastructure / DB growth
2 years - 0 GB -> 200 GB
1 years - 200 GB -> 600 GB
6 months - 600 GB -> 1.2TB
Around 80-100 clients when managing the bare-metal servers started
becoming a task; having already had our fair share of war stories - database
going down; disk failure with RAID; log disk getting full etc.
● Exploding Service > Workers (120)
Multi-threaded / Memory hungry / Isolation

7. Previous Setup (Software stack)
● Database - MS SQL 2014 (1 Big DB)
Typical star schema; mixed load (OLTP / OLAP)
● Asp.NET MVC / Knockout.JS / WCF / Web API
● Over 80-90 Always running background services - processing data from
Google Adwords, Yahoo Bing, Facebook and other external services
including our own ad-serving and tracking infrastructure.

8. Considerations
● Multiple providers
AWS vs. Microsoft Azure
● Cloud vendor Lock-in
Yes that is a term!
● Capacity planning / Cost Estimation / Benchmark
The cloud is a complex beast. Pay per use feels liberating but for consistently
high usage/loads is cloud even apt?

9. AWS vs Azure (Considerations contd.)
● You are bound to be confused

10. Amazon Web Services

11. Microsoft Azure

12. Google Cloud

13. Bakasur Thali

14. Azure
● Microsoft Azure initially was all over the
place; but in the last 2 years it has caught
up and is in a promising direction (same
can be said about Microsoft)
● Our software stack was a ‘first class’
citizen in Azure ecosystem
- Azure SQL Database Pool
- Azure App Service
AWS vs Azure (Considerations contd.)
AWS
● 3+ Experience running a horizontally
auto-scaled Ad-server and Event racking
system with close to 99.998% uptime
● Exposed to the full stack of AWS right
from Route53, ELB, EC2, DynamoDB, S3
and CDN

15. Azure SQL Database Elastic Pool
AWS vs Azure (Considerations contd.)

16. Azure SQL Database Elastic Pool
AWS vs Azure (Considerations contd.)

17. Azure SQL Database Elastic Pool
AWS vs Azure (Considerations contd.)

18. Azure SQL Database Elastic Pool
● Simple, cost-effective solution for managing and scaling multiple databases
that have varying and unpredictable usage demands
● Shared pricing plan
● Ideal for multi-tenant applications - large differences between peak utilization
and average utilization per database.
AWS vs Azure (Considerations contd.)

19. AWS vs Azure (Considerations contd.)
Azure App Service
● Multiple languages and frameworks - App Service has first-class support for
ASP.NET, Node.js, Java, PHP, and Python.
● DevOps optimization - Set up continuous integration and deployment with
Visual Studio Team Services, GitHub, or BitBucket. Promote updates through
test and staging environments
● Global scale with high availability - Scale up or out manually or automatically.

20. ● If you are working on business critical applications - then it’s an important
consideration
● You ideally want the best of what is to be offered by cloud provider
but not get locked in. Unless it suits your need to the tee.
● Having a popular and widely adopted service as managed is a great
advantage - happy that slowly and steadily Azure offers such services - eg:
Redis, HD Insight, Azure SQL
Cloud vendor lock-in (Considerations contd.)

21. ● Pay-per-use is great for on-demand or sporadic usage; for always on
infrastructure being able to benchmark loads and eventually estimate costs
is difficult to get right
● We had cases of Azure DBs capacity planning tool fail on us - not having the
right plan size. We split each tenant to multiple DBs of it’s own
● Migrated tenants in batches and so we were able to benchmark and plan
capacity likewise
Capacity / Cost / Benchmarking (Considerations contd.)

22. Service / Worker VMs
- From 1 big box VM to 25 VMs
Misc Services
- Redis
- CDN
- Cloud storage
Current Setup (Infrastructure)
Azure SQL
- 80 tenants on 1 SQL DB > 480 DBs (4x)
- Hovering around 1 TB; to 2.8TB
Azure App Service
- Web app
- API
- WCF

23. Timeline of Migration
Discussing and evaluation
various ideas
April 2016
Declaration of WAR
June 2016
First live tenant
Mid August
New tenants started using
the cloud stack
Sept 2016
All tenants migrated with
close to 12months data
Dec 2016

24. ● Tooling / Logging / Performance monitoring
We had one problem earlier; now the problem is compounded and spread out
● Keeping all DB schemas in sync (migrations)
● Exception logging; actionable SMS alerts
● Our costs increased 3-5x; also the number of tenants in that time. But we
were able to scale
New Challenges

25. “The cloud is not a silver bullet”
silver bullet ~ noun
‘a simple and seemingly magical solution to a complicated problem’
Twitter: @ak47suve
Email: akshay@deltax.com