fix: expire cached value after 30 seconds from accessing

Mimir.Worker/Client/HeadlessGQLClient.cs

@@ -2,6 +2,7 @@
 using System.Net.Http.Headers;
 using System.Text;
 using System.Text.Json;
+using BitFaster.Caching;
 using BitFaster.Caching.Lru;
 using Libplanet.Crypto;
 using Microsoft.IdentityModel.Tokens;
@@ -17,7 +18,13 @@ public class HeadlessGQLClient : IHeadlessGQLClient
     private readonly Uri[] _urls;
     private readonly string? _issuer;
     private readonly string? _secret;
-    private readonly ConcurrentLru<long, GetTransactionsResponse> _transactionCache = new(10);
+
+    private readonly IAsyncCache<long, GetTransactionsResponse> _transactionCache =
+        new ConcurrentLruBuilder<long, GetTransactionsResponse>()
+            .AsAsyncCache()
+            .WithExpireAfterWrite(TimeSpan.FromSeconds(30))
+            .WithCapacity(10)
+            .Build();
     private const int RetryAttempts = 3;
     private const int DelayInSeconds = 5;