Quick Answer
Transient: new instance created every time the service is requested — for lightweight, stateless services. Scoped: one instance per HTTP request — for DbContext and request-specific services. Singleton: one instance for the app lifetime — for caches, config wrappers, and truly shared services. Injecting a Scoped service into a Singleton causes a captive dependency bug.
Answer
ASP.NET Core's DI container supports three main lifetimes:
Transient – A new instance is created every time it is requested. Best for lightweight, stateless services.
Scoped – One instance per HTTP request. Ideal for services that work with per-request data such as unit-of-work or context services.
Singleton – A single instance is created and shared for the lifetime of the application. Must be thread-safe and used carefully around shared state.
Choosing the wrong lifetime can lead to concurrency bugs, memory leaks, or stale data.
S
SugharaIQ Editorial Team
Verified Answer
This answer has been peer-reviewed by industry experts holding senior engineering roles to ensure technical accuracy and relevance for modern interview standards.
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