Search the practice set
126 questions, 454 terms and 400 topics in 20 areas.
35 results for “First-Principles Reasoning”
First-Principles Reasoning
Reducing a problem to the physical, mathematical or economic facts it rests on, then reasoning up, rather than reasoning from analogy or convention.
Airbnb's Service-Oriented Migration
Airbnb decomposed a large Rails monolith by first extracting a unified data-access layer, so that services were built on owned data rather than on shared database tables.
Graph Database
A store whose first-class citizens are nodes and the relationships between them, making multi-hop traversal cheap.
Hedged Request
Sending a duplicate of a request to a second replica after a short delay and using whichever response returns first, to cut tail latency.
Instagram's Early Scaling
Instagram reached tens of millions of users on Django and PostgreSQL with a handful of engineers, by deliberately choosing boring technology and doing the simple thing first.
Instance Family
A group of instance types sharing a resource profile — general purpose, compute optimised, memory optimised, storage optimised, accelerated — chosen by which resource the workload…
Priority Queueing
Classifying requests by business importance so that overload sheds the least valuable work first rather than an arbitrary slice.
Query Plan
The database's chosen strategy for executing a query, and the first thing to look at when one is slow.
SOLID
Five object-oriented design principles — single responsibility, open/closed, Liskov substitution, interface segregation, dependency inversion.
Systems Thinking
Reasoning about a system in terms of the interactions and feedback loops between its parts, rather than the parts individually.
Try-Confirm-Cancel
A three-phase distributed transaction where each participant first reserves resources, and a coordinator then confirms or cancels all reservations.
eBay's Architectural Generations
eBay rewrote its core platform several times across its first decade, each time because the previous generation had hit a limit that could not be tuned away.
gRPC
A contract-first RPC framework using Protocol Buffers over HTTP/2, with generated clients and servers and first-class streaming.
A critical CVE is announced in a widely-used library. Walk me through the first four hours.
Hour 1 — determine exposure Query the SBOMs across the estate , including transitive dependencies. This is the moment that justifies having them: without, this
A team is launching a new service and asks what its SLO should be. How do you help them decide, and why is "99.99%" usually the wrong first answer?
What the interviewer is testing Whether you treat reliability as a cost benefit decision with a budget, or as a virtue to maximise. Why not four nines It costs
A user in Mumbai types your URL and presses enter. Walk me through every hop until the HTML reaches their browser. Where would you look first if the page were slow?
What the interviewer is testing This is the classic architecture screening question, and it is asked because the answer's depth correlates strongly with real ex
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
Anomalous access to a customer database is detected. Walk me through the first day, and say what determines whether you can answer the regulator.
The first hours Declare an incident and assign command. Named commander who does not debug, operations lead, communications lead, scribe. Security incidents add
Knight Capital lost roughly $460M in 45 minutes in 2012 after a deployment reached seven of eight servers. Which architectural failures made that possible, and which one would you fix first?
The case, as publicly reported Per the SEC's 2013 order, Knight Capital deployed new order routing code to eight production servers ahead of a NYSE programme la
You are asked to lead a migration of 300 applications to cloud. What happens in the first ninety days?
Days 1–30: discovery, and the foundation in parallel Discovery from evidence, not interviews. Network flow logs for dependencies (the only trustworthy source),
You inherit an estate of roughly 400 applications, no reliable inventory, and a mandate to reduce cost and risk. What do you do in the first ninety days?
What the interviewer is testing Whether you can sequence work at portfolio scale, and whether you go for evidence before strategy. This is the enterprise archit
Your service will exceed capacity by 30% during a known peak. Do you shed load or brown out, and how do you decide what goes first?
The decision Brown out first; shed only if that is not enough. They are complementary rather than alternatives, and brownout is strictly less harmful when it is
Your system handles 1,000 requests per second today. Marketing says a campaign will bring 10,000 next month. What breaks first, and how do you find out?
What the interviewer is testing Whether you reason about bottlenecks systematically or start adding servers. The shape of the answer Scaling is not uniform. Som
First-Principles Reasoning
Reducing to physics, mathematics and economics, then reasoning up.
Architecture Principles
Durable agreed rules that rule options out, stated with rationale and implications.
Caching for Performance
Layer choice, hit ratio as a first-class metric, and cold-cache recovery.
Degradation Modes
Deciding in advance what is shed first and what is protected.
Distributed Systems
General material on partial failure, coordination and distributed reasoning.
Horizontal vs Vertical Scaling
Scale out for stateless, scale up first for stateful.
Presenting to Executives
Decision first, cost, risk, and what happens if we do nothing.
SOLID
Five design principles, two of which scale beyond the class.
Stress Testing
Pushing past target to learn what breaks first and how it fails.
gRPC APIs
Contract-first RPC, generated clients and protobuf compatibility rules.