The HLD interviewThe latency ladder
If 1 nanosecond lasted a second, how long is a round trip to Frankfurt?
0%
Page 4
More questions.
Core conceptsWhat counts as down
Your ATM refused you twice, yet the bank says it was up. Who’s right?
0%
Networking and APIsPayments
If UDP is faster, why not send your UPI payment over it?
0%
Data and storageNoisy neighbour
Why can one analyst’s query slow checkout at dinner peak?
0%
Caching fundamentalsWhy distribute
Why does a mithai shop at Diwali need eight counters and stand-ins?
0%
Messaging and streamsReordering
Why does the app say “preparing” for a parcel that already shipped?
0%
Distributed coordinationSplit brain
Two servers both believe they’re the leader. Whose writes count?
0%
Running in productionReplicas vs backups
Why can’t a replica one second behind undo a bad migration?
0%
Why is it slow? Performance anti-patternsThe symptom
Orders are 4% of the writes. Why does checkout slow when telemetry doubles?
0%
SecurityLayers
Your database is encrypted at rest. Why can a SQL injection still read it?
0%
Multi-tenant SaaSTwo questions
You type acme.app.example. How does one SaaS find your company’s data?
0%
Architecture stylesCoupling
Five services at 99.9% each. Why does checkout fail 3.6 hours a month?
0%
System design trade-offsTwo styles
A dosa counter or a biryani token board. Which one is your API?
0%
Key technologiesData modelling
A veg dish under ₹150? Why does Elasticsearch return a restaurant without one?
0%
Common patternsEdge problem
Your nearest restaurant is 700 m away, in a different geohash cell. Now what?
0%
InfrastructureSnowflake IDs
How do 60 machines mint 2 million unique IDs a second without talking?
0%
Search & discoveryWeb search
You type “ipl score”. How do 20 billion pages become ten links?
0%
Storage & mediaPipeline
How does a 20 GB upload become watchable by anyone within minutes?
0%
Social & feedsFor You
How does TikTok pick your next 8 videos from a billion in 150 ms?
0%
Real-time & collaborationMerging
Four students edit one report at 1 a.m. Why does nobody’s typing vanish?
0%
Location & mapsDispatch
Your biryani needs 15 more minutes. When should the rider set off?
0%
E-commerce & bookingDouble booking
Two fans tap seat C-K-14 in the same second. Who gets it?
0%
Payments & fintechFairness
Two orders reach two gateways at once. Who decides which came first?
0%
Data, analytics & monitoringThe funnel
A billion clips and a fifth of a second. How is yours picked?
0%
Developer platformsIsolation
1,250 companies’ tickets share one table. What stops a leak?
0%
AI & LLM systemsToken limits
50 tokens or 100,000: both are “one request”. So what should a limit count?
0%