Search the practice set
275 questions, 991 terms and 600 topics in 30 areas.
60 results for “Performance Test Design”
Arrival Rate Model
Driving a load test by requests arriving per second regardless of how the system responds, rather than by a fixed number of virtual users.
Testability as a Design Property
How cheaply a system's behaviour can be observed and controlled, which is decided by architecture and largely fixed before any test is written.
Assumption Excavation
Deliberately surfacing the unstated beliefs behind a design or a requirement, to test which are constraints and which are merely habits.
Application Performance Monitoring
Instrumentation inside the application that attributes latency and errors to specific code paths, queries and dependencies.
Boundary Volatility Test
Evaluating a proposed service boundary by asking whether the things on either side change for different reasons and at different rates.
Control Test Automation
Executing a control's test continuously against the whole population rather than sampling it annually, which changes both the detection latency and the strength of the evidence.
Design Review Trigger
The stated conditions under which a change requires security review, so that review capacity goes to what warrants it and everything else proceeds.
Differentiation Test
The question of whether a capability is a source of competitive advantage, used as the primary filter in build-versus-buy decisions.
Domain-Driven Design
Modelling software around the business domain, with boundaries drawn where the language of the business changes.
End-to-End Test Cost Curve
How the cost of a broad end-to-end suite grows with its size while its marginal value falls, and where the two cross.
Performance Budget
A stated numeric limit on a performance characteristic, enforced automatically so that regressions fail a build rather than accumulating.
Performance Budget Enforcement
A stated limit on bundle size or a timing metric that fails a build when exceeded, which is what turns performance from a periodic project into a constraint.
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
Mobile conversion is 40% below desktop. Product blames the design; analytics shows users leaving before the page is usable. How do you investigate?
Get field data before touching anything A laboratory run on a developer machine measures one configuration, usually the fastest one anyone uses. Real traffic in
A DR test fails: the secondary region cannot launch enough instances. What happened, and what standing checks prevent it?
What happened Service quotas in the secondary region are far lower than in the primary , because nothing has ever run there at scale. Quotas are per account and
A core mainframe system with no API supports nightly batch file exchange only. The business needs near-real-time order status. Design the integration.
Establish the real constraint "No API" usually means no API the mainframe team will build on your timeline . Find out what exists: message queue interfaces, dat
A design review presents a new event-driven platform. What cost questions do you ask before approving it?
What the interviewer is testing Whether cost is part of your architecture review or an afterthought handled by finance later, and whether you know the specific
A payments API must guarantee that a network retry never charges a customer twice. Design the mechanism end to end.
Why this is unavoidable A client that times out on a POST cannot know whether the request succeeded. Not retrying risks a lost payment; retrying risks a duplica
A platform of 40 services has logs only, and incidents take hours to diagnose. Design the observability strategy and its rollout order.
Why logs alone fail at this size Logs answer "what happened in this service". They cannot answer "where did this request spend its time across twelve services",
A regulated client requires that no traffic between their data centre and your SaaS platform traverses the public internet. Design the connectivity and justify the cost.
Two distinct requirements hiding in one sentence Traffic must not traverse the public internet — a routing requirement. The client must be able to demonstrate i
A team shows you a design with eight services. Without knowing the domain, what questions tell you whether the boundaries are right?
What the interviewer is testing Whether you can evaluate a structure from its properties rather than needing to be a domain expert in every system you review. T
A twenty-year-old core system supports most of the business. It is on unsupported technology, three people understand it, and the last replacement attempt was abandoned after two years. Design the programme.
Learn from the abandoned attempt first The most important input is why the last one failed, and the reasons are usually structural rather than technical: a big
An estate has database passwords in environment variables across 200 services. Design the migration to a secrets manager.
Sequence it by risk, not by convenience Phase 0 — stop the bleeding. Secret scanning in CI and on the existing repositories, blocking new commits containing cre
Architecture decisions in your organisation are either ignored or bottlenecked in a review board. Design something better.
Why both failure modes have the same cause A review board is a synchronous, low bandwidth, high latency channel: teams wait, decisions are made by people distan
Classify DynamoDB, Spanner and Cassandra under PACELC, and say which half of the classification you would actually design around.
The classifications Store Partition Else Why DynamoDB (default reads) PA EL Serves from any replica; eventually consistent reads avoid a quorum round trip Cassa
Design a URL shortener handling 100 million new links per month and 10 billion redirects. Where is the real difficulty?
What the interviewer is testing The classic warm up. What is being assessed is not whether you can shorten a URL — it is whether you do capacity arithmetic befo
Design a webhook delivery system for a platform with 10,000 customers. What are the hard parts?
Delivery, and its failure modes Persist the event first, deliver asynchronously. Delivery in the request path couples your latency and availability to every cus
Design an order submission API that is safe when the client cannot tell whether its request succeeded. What exactly do you store, and when?
What the interviewer is testing Whether you know that "make it idempotent" is a design with specific failure modes, not a checkbox. The core design The client g
Design rate limiting for a multi-tenant API where a single customer's traffic spike currently degrades service for everyone.
Name the problem precisely This is the noisy neighbour problem. Rate limiting is one control for it, and on its own it is incomplete — a customer within their l
Design the audit logging for a system handling financial transactions. What is logged, where does it go, and what makes it hold up?
What is logged Significant actions only , defined explicitly rather than logging everything — an audit trail nobody can search is not usable evidence: Authentic
Design the network layout for a three-tier application in one cloud region. What are the decisions you cannot easily change later?
What the interviewer is testing Whether you know which network decisions are cheap and which are effectively permanent. This is a knowledge question with a clea
Design the timeout configuration for a request that passes through gateway, orders, pricing and inventory. What numbers, and what rule generates them?
The rule that generates the numbers One budget at the edge, decreasing inward, with room for a retry at exactly one layer. Start from what the caller will actua
In a design review, a respected senior engineer proposes an approach you believe is wrong. The room defers to them. How do you handle it?
What the interviewer is testing Whether you can be effective without authority, which is most of the architect's job. It is also testing whether you assume you
Incidents at your company are chaotic: unclear ownership, no communication, and postmortems that produce nothing. Design the improvement.
Roles, so that coordination exists The failure is everyone investigating and nobody coordinating. Ten people debugging is slower than three debugging and one di
Leadership asks for "five nines" across the platform. Engineering says it is impossible. Design the response.
Reframe the request "Five nines" is almost never what the business actually wants. 26 seconds of downtime per month is a number chosen for its rhetorical weight
Maersk rebuilt roughly 4,000 servers and 45,000 PCs in about ten days after NotPetya in 2017, and recovered its directory only because one data centre had been offline during the attack. What does this say about DR design?
The case, as publicly reported In June 2017 the NotPetya malware — destructive rather than financially motivated — propagated through Maersk's network, encrypti
Netflix built its own CDN; Dropbox moved storage off S3. Both are usually wrong. What conditions made them right, and how do you test for those conditions?
What the interviewer is testing Whether you can extract the conditions from a famous decision rather than the decision itself. These two cases are the most comm
Performance Test Design
Workload models, warm-up, think time, and the distribution the average hides.
Application Performance Monitoring
Attributing latency to code paths, queries and dependencies.
CDC Pipeline Design
Building on a change stream: snapshot plus delta, tombstones, and merge into the target.
Caching for Performance
Layer choice, hit ratio as a first-class metric, and cold-cache recovery.
Chaos as a Test
Fault injection with a hypothesis, a blast radius and an abort condition.
Control Design vs Operation
A control that is well designed and never runs fails exactly like one that is absent.
Database Performance
Plans, indexes, contention and the pool in front of the database.
Design Authority
How an ARB should decide, what it should not review, and how it avoids becoming a queue.
Design Patterns
Reusable solutions at code level, and when they become ceremony.
Design Systems
Components as a versioned internal product, with adoption and deprecation like any API.
Domain-Driven Design
Ubiquitous language, bounded contexts and context mapping.
End-to-End Test Economics
Why broad end-to-end suites get slow, flaky and abandoned, and what to keep.
Flaky Test Management
Quarantine, detection, and the trust a suite loses once red stops meaning broken.
Human-in-the-Loop Design
Meaningful review rather than a rubber stamp, and designing against automation bias.
Integration Test Boundaries
What sits inside a test's boundary, what is faked, and the confidence that follows.
Network Performance
Latency floors, bandwidth-delay product, and what no code change fixes.
Network Performance Tuning
Keep-alive, compression, payload size and round-trip elimination.
Non-Functional Test Strategy
Testing availability, latency, security and recovery rather than only behaviour.
Performance & Capacity
General material on performance and capacity engineering.
Performance Budgets
Targets enforced in CI so regressions fail the build.
Performance vs Cost
Buying latency, and knowing what the last millisecond is worth.