AZ-305 · Data and Storage

Storage account tiers

Tier	Availability	Read latency	Cost	Rehydrate
Hot	Online	ms	$$$	—
Cool	Online	ms	$$	—
Cold	Online	ms (higher)	$	—
Archive	Offline	Hours	¢	Up to 15 hours

{
  "rules": [
    {
      "enabled": true,
      "name": "tier-and-archive",
      "type": "Lifecycle",
      "definition": {
        "filters": { "blobTypes": ["blockBlob"] },
        "actions": {
          "baseBlob": {
            "tierToCool":    { "daysAfterModificationGreaterThan": 30 },
            "tierToArchive": { "daysAfterModificationGreaterThan": 180 },
            "delete":        { "daysAfterModificationGreaterThan": 365 }
          }
        }
      }
    }
  ]
}

SQL flavors — the trade-off

Azure SQL Database

Single database, fully managed. Elastic pools share DTUs/vCores across DBs. No cross-DB queries — think one micro-service, one DB.

Azure SQL Managed Instance

Nearly full SQL Server surface — cross-DB queries, SQL Agent, CLR. Deployed inside your VNet. The lift-and-shift answer.

SQL Server on VM (IaaS)

You own the OS + patching + backups. Only pick this when the exam says something the PaaS services can’t do (double-hop Kerberos, specific extended events, etc.).

Cosmos DB consistency levels

Cosmos DB questions almost always hinge on consistency. Here they are, strongest to weakest:

Level	Guarantees	Use when
Strong	Linearizable	Financial ledgers, unique counters
Bounded staleness	Reads lag writes by $\le k$ operations or $t$s	Feed timelines, leaderboards
Session	Read-your-own-writes for a client session	User profiles (default)
Consistent prefix	Reads never see gaps in write order	Chat replay
Eventual	Weakest, cheapest, highest throughput	Analytics, IoT ingest

Redundancy shorthand

Acronym	Copies	Fault domain
LRS	3 within one DC	Rack failure
ZRS	3 across AZs	Data-center failure
GRS	LRS + async to paired region	Region failure (RPO ~ minutes)
RA-GRS	GRS + read from secondary	Region failure + read-only DR
GZRS	ZRS + async to paired region	AZ + region failure

Backup decision matrix

Azure Backup vault with soft-delete + versioning + immutability policies.
For long-term regulatory holds, combine with legal hold on the container.