Search the practice set
126 questions, 454 terms and 400 topics in 20 areas.
41 results for “Availability Zones”
Cross-Zone Data Transfer
Charges incurred when data moves between availability zones within a region — invisible on architecture diagrams and a recurring surprise on cloud bills.
Zonal vs Regional Services
Whether a cloud resource lives in one availability zone or is inherently spread across several — a property that determines what a zone failure takes with it.
Availability Calculation
Deriving a system's availability from its components, remembering that dependencies in series multiply.
Availability Zone
One or more physically separate data centres inside a cloud region, with independent power, cooling and network, connected by low-latency links.
Durability vs Availability
Two different storage guarantees — whether data survives, and whether it can be reached right now — routinely conflated because both are quoted in nines.
Account Vending
Automated creation of new cloud accounts pre-configured with the organisation's networking, identity, logging, guardrails and cost allocation.
Anycast
Advertising the same IP address from many locations, so the network routes each client to the topologically nearest one.
Blast Radius Reduction
The set of deliberate partitions — accounts, regions, zones, cells, tenants, deployment stages — that bound how far any single failure or compromise can reach.
CAP Theorem
During a network partition a distributed system must choose between consistency and availability; it cannot have both.
Cost vs Reliability Trade-off
The non-linear relationship between availability and spend, which makes each additional nine roughly an order of magnitude more expensive.
Cross-Zone Load Balancing
Whether a load balancer node distributes traffic to targets in all zones or only its own — a setting that affects both balance and data transfer cost.
Egress Cost
The charge for moving data out of a cloud provider or across its zones and regions — usually the least-anticipated line on a cloud bill.
Harvest and Yield
A refinement of CAP that treats availability as a continuum — yield is the fraction of requests answered, harvest is the fraction of data reflected in an answer.
Image Registry
The store from which container images are pulled, and an under-appreciated availability and security dependency of every deployment and every autoscale event.
Leader Election
The process by which a group of nodes agrees which one of them is currently in charge of a task that must not run twice.
Managed Service Upgrade Window
The period during which a provider may apply patches or version upgrades to a managed service, usually involving a failover or brief unavailability.
Message Queue
A store that holds messages until a consumer processes them, decoupling producer availability and rate from consumer availability and rate.
Microsegmentation
Enforcing fine-grained network policy between individual workloads rather than between broad network zones, so a compromise cannot move laterally.
Non-Functional Requirement
A requirement about how well the system must behave rather than what it must do — latency, availability, throughput, security, cost.
PACELC
An extension of CAP that also describes the normal case — if Partitioned choose Availability or Consistency, Else choose Latency or Consistency.
Redundancy
Having more instances of a component than the load requires, so that failures can be absorbed without loss of service.
Service Control Policy
An organisation-level guardrail that limits what any identity in an account may do, regardless of the permissions granted within that account.
Slack's Cellular Migration
After repeated availability-zone-level incidents, Slack rebuilt its infrastructure into per-zone cells with the ability to drain traffic away from a failing zone in minutes.
Split Vote
An election in which no candidate obtains a majority, so the term ends with no leader and the process must repeat.
Strong vs Eventual Consistency
A per-operation decision, not a per-system one: whether this specific read must reflect every completed write.
Subnet
A subdivision of a network's address range, used as the unit of routing and, in cloud, of availability-zone placement.
Synchronous vs Asynchronous Communication
Whether the caller waits for the callee's answer — decided by whether the caller's outcome depends on it, not by latency or taste.
One availability zone becomes unavailable. Walk through what happens to a typical three-tier application and what you would have changed.
What survives and what does not Load balancer — regional, survives, and stops routing to targets in the failed zone once health checks fail. Note the detection
A card payment authorisation service runs active-active across two regions. A network partition splits them. Do you keep accepting authorisations, and what breaks either way?
What the interviewer is testing Whether you can apply CAP to a domain where the cost of each choice is concrete, and whether you recognise that "it depends" has
A product catalogue page does 40,000 reads per second against a database that can serve 5,000. Walk me through the caching design, including what happens at 3 AM when the cache is empty.
What the interviewer is testing Whether you can design a cache including its failure modes, rather than saying "put Redis in front of it". The base design Cache
An order service must notify inventory, billing, shipping and analytics when an order is placed. Synchronous calls or events? Justify your choice per consumer.
What the interviewer is testing Whether you apply the decision per interaction rather than adopting one style globally. The framing that matters Synchronous cal
An organisation is starting cloud adoption. Three teams want to deploy next month. What must exist first, and what can wait?
What must exist before anything reaches production Account structure. Separation by environment and by workload, because an account is the strongest isolation b
When should a service call another synchronously, and when should it publish an event instead? Give me the deciding test, not a preference.
The deciding test Does this user action succeed or fail based on this callee's response? If yes, the call is synchronous, because you need the answer to decide.
You run active-active across two regions. The link between them fails. What should each region do, and what would you have designed differently?
The immediate answer Neither region can safely keep accepting writes to shared state, because neither can know it is the surviving side. Each sees one of two no
Your service registry becomes unavailable. Every service is healthy. What happens, and what should happen?
What usually happens A total outage , despite every service being fine — because resolution is on the request path and a failed resolution fails the request. Th
Availability Zones
The unit of correlated physical failure, and what zones do not protect against.
Availability Mathematics
Series dependencies multiplying, and redundancy that is not independent.
Landing Zones
A governed foundation of accounts, network, identity and guardrails.
Fault Isolation
Cells, zones, tenants and the partitions that bound a failure.
Quality Attributes
Availability, latency, throughput, security, cost — expressed as testable scenarios.
Reliability vs Complexity
Mechanisms that add availability and add failure modes.