What is ResultSet Caching?
💡 Concept Name
ResultSet Caching – A technique where the results of a database query are stored in memory or temporary cache to improve performance on repeated queries.
📘 Quick Intro
Instead of re-executing the same SQL query repeatedly, ResultSet Caching allows reuse of previously computed query results, reducing DB load and latency.
🧠 Analogy / Short Story
Imagine checking the same weather report five times an hour. Instead of asking the satellite each time, you keep the latest report on your fridge for reuse — that’s result caching.
🔧 Technical Explanation
- ⚙️ Caches query outputs (rows/data) in memory or local cache store.
- 🕒 Useful for read-heavy and slow-changing data scenarios.
- 🧠 Supported by many ORMs and databases (EF, Hibernate, Oracle, Redis, etc.).
- 📉 Reduces I/O, query parsing, and CPU time on the DB server.
- ♻️ Must manage cache invalidation when data changes.
🎯 Purpose & Use Case
- ✅ Dashboards or reports with frequent queries.
- ✅ Autocomplete or filtered search suggestions.
- ✅ Read-heavy REST APIs returning similar responses.
💻 Real Code Example
// Using MemoryCache to cache resultset of a query
public class ProductService
{
private readonly IMemoryCache _cache;
private readonly DbContext _context;
public ProductService(IMemoryCache cache, DbContext context)
{
_cache = cache;
_context = context;
}
public List<Product> GetCachedProducts()
{
return _cache.GetOrCreate("AllProducts", entry =>
{
entry.AbsoluteExpirationRelativeToNow = TimeSpan.FromMinutes(5);
return _context.Products.ToList();
});
}
}
❓ Interview Q&A
Q1: What is ResultSet Caching?
A: Storing query results to avoid recomputing the same results repeatedly.
Q2: Why is it useful?
A: Reduces DB hits, improves response time, and scales better.
Q3: When should it not be used?
A: When data changes frequently or needs to always be fresh.
Q4: What tools support it?
A: EF Core, Hibernate, Redis, Oracle, etc.
Q5: What is a risk in ResultSet Caching?
A: Serving stale or outdated data if not invalidated.
📝 MCQs
Q1. What is cached in resultset caching?
- SQL command
- Query result
- Table schema
- Connection string
Q2. What kind of data is best for result caching?
- Frequent updates
- Rarely changing data
- Binary files
- Streaming logs
Q3. Which .NET class is used for in-memory caching?
- IDataCache
- MemoryBuffer
- IMemoryCache
- QueryContext
Q4. What is a drawback of result caching?
- Slower queries
- May return stale data
- More CPU usage
- Larger DB size
Q5. Which strategy updates cache when data changes?
- Data backup
- Cache invalidation
- Eager loading
- Streaming
Q6. Which technology is commonly used for distributed cache?
- LINQ
- Redis
- EF Core
- Blazor
Q7. What happens when cache expires?
- Nothing
- New query is executed
- App crashes
- Cached forever
Q8. What improves cache accuracy?
- Adding RAM
- Avoiding LINQ
- Expiration and refresh logic
- Logging queries
Q9. ResultSet caching is most helpful in...
- Write-heavy apps
- Read-heavy apps
- Gaming servers
- File transfers
Q10. Which design pattern does it follow?
- Factory
- Cache-aside
- Mediator
- Repository
💡 Bonus Insight
ResultSet caching can massively reduce DB cost in high-load scenarios, but needs careful invalidation strategy for consistency.
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