Small tweaks for caching limits

instructions/cache-usage.md

@@ -51,7 +51,7 @@ var entryOptions = new MemoryCacheEntryOptions()
     .SetSize(1);
 ```
 
-   In the code: `Program.cs` registers the cache with `SizeLimit` taken from the `TextServices:CacheMaxEntries` setting (default 20; read directly from configuration because options binding isn't available at that point in startup). `TextCache` sets `.SetSize(1)` on every entry — both `Text` and `AutoComplete` objects share the same slot budget.
+   In the code: `Program.cs` registers the cache with `SizeLimit` taken from the `TextServices:CacheMaxEntries` setting (default 20; read directly from configuration because options binding isn't available at that point in startup). The config key is looked up via `nameof(SearchApiOptions.CacheMaxEntries)` rather than a string literal, so the `SearchApiOptions` property — otherwise unreferenced in code, since this path bypasses options binding — stays in lockstep with the setting it documents. `TextCache` sets `.SetSize(1)` on every entry — both `Text` and `AutoComplete` objects share the same slot budget.
 
 2. **Add an absolute expiration floor.** ✅ **Implemented.** Sliding expiration alone means a popular text stays cached forever. Adding an absolute cap forces periodic refresh and bounds LOH lifetime. `TextCache` applies `.SetAbsoluteExpiration()` from the `TextServices:CacheAbsoluteExpirationHours` setting (default 4 hours) alongside the sliding expiration.
 

src/TextServices.Search.Api/Configuration/SearchApiOptions.cs

@@ -14,10 +14,11 @@ public class SearchApiOptions
     public int CacheSlidingExpirationMinutes { get; set; } = 30;
 
     /// <summary>
-    /// Absolute expiration cap for cached objects (hours).
+    /// Absolute expiration cap for cached objects (hours). Fractional values are allowed
+    /// (e.g. 0.25 for 15 minutes), for deployments that need a tighter cap than whole hours.
     /// Prevents popular texts from staying in the LOH indefinitely.
     /// </summary>
-    public int CacheAbsoluteExpirationHours { get; set; } = 4;
+    public double CacheAbsoluteExpirationHours { get; set; } = 4;
 
     /// <summary>
     /// Maximum number of Text objects to hold in the memory cache simultaneously.

src/TextServices.Search.Api/Program.cs

@@ -97,7 +97,8 @@
 // ---- Cache ------------------------------------------------------------------
 
 builder.Services.AddMemoryCache(opts =>
-    opts.SizeLimit = builder.Configuration.GetSection("TextServices").GetValue<int?>("CacheMaxEntries") ?? 20);
+    opts.SizeLimit = builder.Configuration.GetSection("TextServices")
+        .GetValue<int?>(nameof(SearchApiOptions.CacheMaxEntries)) ?? 20);
 builder.Services.AddSingleton(new AsyncKeyedLocker<string>());
 builder.Services.AddSingleton<ITextCache, TextCache>();