Search the practice set
126 questions, 454 terms and 400 topics in 20 areas.
60 results for “Network Performance Tuning”
Application Performance Monitoring
Instrumentation inside the application that attributes latency and errors to specific code paths, queries and dependencies.
Content Delivery Network
A geographically distributed cache that serves content from a location near the user instead of from the origin.
Anycast
Advertising the same IP address from many locations, so the network routes each client to the topologically nearest one.
Availability Zone
One or more physically separate data centres inside a cloud region, with independent power, cooling and network, connected by low-latency links.
Bloom Filter
A compact probabilistic structure that answers "is this key definitely absent, or possibly present?" — no false negatives, tunable false positives.
Bloom Filter Cache Guard
Placing a Bloom filter in front of an expensive lookup so that keys which certainly do not exist never reach it.
Burstable Instance
An instance that provides a low baseline CPU allocation and accrues credits while idle, spendable for short periods of full performance.
CAP Theorem
During a network partition a distributed system must choose between consistency and availability; it cannot have both.
Cache Invalidation
The problem of removing or refreshing cached data when the underlying source changes, and the reason caching is harder than it looks.
Caching Strategy
The chosen pattern for how a cache is populated, read and invalidated — cache-aside, read-through, write-through or write-behind.
Cardinality Estimation
The planner's prediction of how many rows each step of a query will produce — the input that determines every other choice it makes.
Concurrency
The number of operations in progress at once — distinct from parallelism, which is how many are literally executing simultaneously.
Connection Pool
A fixed set of reusable database connections shared by an application's requests, and one of the most common hidden capacity ceilings.
Covering Index
An index that contains every column a query needs, so the query is answered from the index without reading the table at all.
DORA Metrics
Four measures of software delivery performance — deployment frequency, lead time for change, change failure rate, and time to restore service.
Database Index
A secondary structure that lets the engine find rows without scanning, trading write cost and storage for read speed.
Denormalisation
Deliberately duplicating data across records to make reads cheap, accepting the write-time cost of keeping copies in step.
Egress Filtering
Restricting which destinations a workload may connect to outbound — the control that limits data exfiltration and SSRF impact, and the one most often omitted.
Egress Path Analysis
Tracing where data physically moves in an architecture, because transfer charges follow paths that appear nowhere on the diagram.
Encryption at Rest and in Transit
Protecting stored data from disclosure if the medium is obtained, and network data from disclosure if the path is observed — two different controls against two different threats.
Failure Threshold
The condition that trips a circuit breaker — best expressed as a failure rate over a rolling window with a minimum request volume, not as a consecutive-failure count.
Global Traffic Management
The layer that decides which region a given user reaches, using DNS, anycast or an edge network, and that performs regional failover.
Google Maps and Planetary-Scale Spatial Serving
Map serving is fast because almost nothing is computed on request — the world is precomputed into a pyramid of tiles, and space is indexed onto a one-dimensional curve.
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.
Horizontal vs Vertical Scaling
Adding more machines versus making one machine bigger — and the fact that vertical is underrated for stateful tiers.
Indexing Strategy
Choosing the set of indexes a table carries by working backwards from its actual queries, and accepting the write cost that each one adds.
Join Strategies
The three ways a database combines two row sets — nested loop, hash join and merge join — and the conditions under which each is correct.
Little's Law
In a stable system, the average number of items in it equals the arrival rate times the average time each spends in it — L = λW.
Load Testing
Driving a system with realistic traffic at a target volume to verify it meets its performance targets before real users do.
Materialized View
A precomputed, stored result of a query, refreshed on a schedule or from a change stream, read instead of recomputing.
Microsegmentation
Enforcing fine-grained network policy between individual workloads rather than between broad network zones, so a compromise cannot move laterally.
A 43-second network partition caused GitHub over 24 hours of degraded service in 2018. How does a 43-second event become a day-long incident?
The case, as publicly reported On 21 October 2018, routine maintenance replacing failing optical equipment caused a 43 second loss of connectivity between GitHu
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 client wants an assistant that answers questions from 50,000 internal documents which change weekly. RAG or fine-tuning? What actually determines the quality?
What the interviewer is testing Whether you understand what each technique actually does, and whether you know that RAG quality is a retrieval problem. Why RAG
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
In July 2019 a single regex deployed globally took Cloudflare's network to 100% CPU within seconds. What does this say about how configuration should be released?
The case, as publicly reported On 2 July 2019, Cloudflare deployed a new managed WAF rule. It contained a regular expression that caused catastrophic backtracki
A dashboard query that took 200ms now takes 40 seconds. The table has grown to 200 million rows. Walk me through diagnosis and fix, including what you would not do.
What the interviewer is testing Whether you diagnose with evidence before changing anything, and whether you know the costs of the fixes you propose. Diagnosis,
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
A table has 14 indexes and writes have become slow. How do you decide which to remove?
The approach 1. Get usage statistics, not opinions. Every major engine reports index scan counts — PostgreSQL's pg stat user indexes , SQL Server's sys.dm db in
Network Performance Tuning
Keep-alive, compression, payload size and round-trip elimination.
Network Performance
Latency floors, bandwidth-delay product, and what no code change fixes.
Application Performance Monitoring
Attributing latency to code paths, queries and dependencies.
Caching for Performance
Layer choice, hit ratio as a first-class metric, and cold-cache recovery.
Database Performance
Plans, indexes, contention and the pool in front of the database.
Network & Egress Costs
Cross-zone and cross-region transfer that appears on no diagram.
Network Security
Segmentation, egress control and limiting lateral movement.
Network Troubleshooting
Flow logs, packet paths, and localising a problem to a hop.
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.
Bottleneck Analysis
Finding the constraint, and expecting a second one behind it.
Capacity Modelling
Arithmetic before load tests, and headroom for failure as well as peak.
Concurrency
Operations in flight, and the limits that are the real capacity ceiling.
Connection Pooling
The most common hidden ceiling, and the metric nobody collects.
Horizontal vs Vertical Scaling
Scale out for stateless, scale up first for stateful.
Landing Zones
A governed foundation of accounts, network, identity and guardrails.
Latency
Distributions rather than averages, and the floors physics imposes.
Little's Law
L = λW, and the pool sizes it computes directly.
Load Testing
Realistic data, realistic mix, and a ramp rather than a step.