Scale-out web apps on Basic, Standard and Premium tiers to 3, 10 and 20 instances respectively. Scale-up to provide additional resource to each instance with higher tiers increasing the limit. Azure SQL also offers Elastic Scale to scale horizontally (sharding) and vertically (250GB Standard, 500GB Premium).
CDN allows content to be replicated globally to be served up to users faster. Files are cached in local Azure Blob storage and accessed using the CDN address. This does not need to be considered when designing web applications which may refer to the original address.
Traffic Manager enables websites to be deployed to multiple regions and accessed using a single URL.
SQL Sync is a feature of Azure SQL which sychronises a database or select tables and columns on a schedule from the source to a HUB database which could be in Azure or on-premise. SQL Sync does not synchronise transactions.
SQL geo-replication allows recovery of a database to another Azure region. Standard tier provides an offline secondary, Premium tier provides up to 4 readable backups.
Web Apps allow a single backup of websites per day, Premium allows up to 50 backups per day. Web App backups will save Web App files, associated database, log files from the website and WebJobs. With Free and Basic FTP(S) or a GIT Clone URL can be used as an alternative.
When designing the data tier it is important to consider the data storage type and scaling of the data:
- Use of relational (RDBMS) e.g. SQL or non-relational database (e.g. Azure Table Storage, DocumentDB)
- Scale, size of database supported
- Normalization of data vs. performance of too many linked tables
- Backup of historic data to reduce security exposure and database size