Drills

.NETASP.NET CoreC#EF CoreSQL

Build a safe filtered list endpoint

Implements bounded filtering and deterministic keyset pagination without accepting arbitrary query expressions.

Coding problemEasy~15 min

Build a typed create-resource endpoint

Creates a resource through an explicit request DTO and returns typed 201, 409, and validation outcomes.

.NETASP.NET CoreC#EF Core

Build daily order KPIs with conditional aggregation

Builds several daily business metrics in one grouped query while keeping each metric definition explicit.

SQLSQL Server

.NETASP.NET CoreEF CoreSQLSQL Server

Build dynamic EF Core filters without client-side evaluation

Explains composing dynamic LINQ filters while keeping query execution in SQL and index-friendly.

Calculate a running account balance

Uses an ordered window aggregate to calculate a deterministic running balance per account.

SQLSQL Server

Calculate invoice total with discounts

Implements invoice total calculation with quantity, unit price, percentage discount, and rounding.

Coding problemHard~35 min

Calculate seven-day rolling revenue

Combines daily aggregation, a calendar table, and a window frame to calculate true seven-calendar-day revenue.

SQLSQL Server

CancellationToken in ASP.NET Core

Use CancellationToken to stop wasted work when clients disconnect, timeouts expire, or background operations are being shut down.

.NETASP.NET CoreC#

.NETApplication InsightsASP.NET CoreEF CoreOpenTelemetry+3

Capture dependency telemetry for SQL, Redis, and HTTP calls

Explains dependency duration, error rate, timeout rate, query tagging, Redis latency, HTTP downstream calls, and endpoint correlation.

Choose an interface or abstract base class in C#

Chooses contracts and shared implementation based on substitutability, state ownership, evolution, and inheritance constraints.

Concept questionEasy~5 min

Choose a TTL and expiration strategy for cached data

Explains how TTL choices balance freshness, load reduction, user expectations, and operational safety.

.NETASP.NET CoreRedisStackExchange.Redis

Comparison questionMedium~8 min

Choose between a GC dump and a full process dump

Chooses heap-focused GC evidence or complete process state based on memory growth, roots, hangs, crashes, locks, and collection risk.

.NET

Concept questionEasy~5 min

Choose between an array, List<T>, and LinkedList<T> in C#

Chooses a sequential collection from size, mutation, access pattern, memory locality, and the behavior callers actually need.

Choose between Join, ToLookup, and repeated scans

Avoids hidden quadratic work by indexing repeated matches while preserving duplicate, missing, ordering, and memory semantics.

Choose between mocks, stubs, fakes, and real dependencies

Compares test doubles by purpose and explains when a real dependency provides a more trustworthy test.

.NETC#xUnit

Choose between records, classes, and record structs

Chooses a type shape from identity, value semantics, mutation, copy cost, default values, and serialization boundaries.

Architecture scenarioHard~12 min

Choose consistency and availability trade-offs

Maps business invariants and stale-data tolerance to strong or eventual consistency, explicit failure behavior, reconciliation, and user-visible state.

.NETASP.NET CoreSQL Server

Choose constructors, static factories, and builders

Creates valid objects with clear intent while choosing construction patterns proportionally to optional data, validation, and lifecycle complexity.

Architecture scenarioMedium~10 min

Choose HTTP status codes for real API outcomes

Maps creation, updates, asynchronous work, validation, authorization, conflicts, and failures to useful HTTP outcomes.

.NETASP.NET Core

.NETApplication InsightsASP.NET CoreAzureAzure App Service+1

Choose rollback, roll-forward, or kill switch during incidents

Compares rollback, roll-forward, feature kill switches, scaling, and degraded mode as incident mitigations.

Application InsightsAzureAzure DevOpsGitHub Actions

Choose rolling, blue-green, or canary deployment

Chooses a deployment strategy from capacity, compatibility, risk, observability, and rollback needs, then defines progressive promotion and abort signals.

Choose Strategy, Adapter, and Decorator for real problems

Selects small structural and behavioral patterns from the problem being solved instead of pattern-name recognition.

.NETASP.NET Core

Choose string comparers for keys, membership, and sorting

Separates ordinal identity comparison from culture-aware display ordering and keeps hash-based collection semantics consistent.

.NETASP.NET CoreC#EF CoreSQL+2

Choose Testcontainers, SQLite, or EF Core InMemory

Chooses database test infrastructure by the provider behavior a test must prove.