diff --git a/org.hl7.fhir.r5/src/main/java/org/hl7/fhir/r5/context/TerminologyCache.java b/org.hl7.fhir.r5/src/main/java/org/hl7/fhir/r5/context/TerminologyCache.java
index f63fbce99..ae60d7fcc 100644
--- a/org.hl7.fhir.r5/src/main/java/org/hl7/fhir/r5/context/TerminologyCache.java
+++ b/org.hl7.fhir.r5/src/main/java/org/hl7/fhir/r5/context/TerminologyCache.java
@@ -133,7 +133,7 @@ public class TerminologyCache {
     json.setOutputStyle(OutputStyle.PRETTY);
     ValueSet vsc = getVSEssense(vs);
     try {
-      ct.request = "{\"code\" : "+json.composeString(code, "code")+", \"valueSet\" :"+(vsc == null ? "null" : json.composeString(vsc))+(options == null ? "" : ", "+options.toJson())+"}";
+      ct.request = "{\"code\" : "+json.composeString(code, "code")+", \"valueSet\" :"+(vsc == null ? "null" : extracted(json, vsc))+(options == null ? "" : ", "+options.toJson())+"}";
     } catch (IOException e) {
       throw new Error(e);
     }
@@ -141,6 +141,16 @@ public class TerminologyCache {
     return ct;
   }
 
+  public String extracted(JsonParser json, ValueSet vsc) throws IOException {
+    String s = null;
+    if (vsc.getExpansion().getContains().size() > 1000 || vsc.getCompose().getIncludeFirstRep().getConcept().size() > 1000) {      
+      s = Integer.toString(vsc.hashCode()); // turn caching off - hack efficiency optimisation
+    } else {
+      s = json.composeString(vsc);
+    }
+    return s;
+  }
+
   public CacheToken generateValidationToken(ValidationOptions options, CodeableConcept code, ValueSet vs) {
     CacheToken ct = new CacheToken();
     for (Coding c : code.getCoding()) {
@@ -151,7 +161,7 @@ public class TerminologyCache {
     json.setOutputStyle(OutputStyle.PRETTY);
     ValueSet vsc = getVSEssense(vs);
     try {
-      ct.request = "{\"code\" : "+json.composeString(code, "codeableConcept")+", \"valueSet\" :"+json.composeString(vsc)+(options == null ? "" : ", "+options.toJson())+"}";
+      ct.request = "{\"code\" : "+json.composeString(code, "codeableConcept")+", \"valueSet\" :"+extracted(json, vsc)+(options == null ? "" : ", "+options.toJson())+"}";
     } catch (IOException e) {
       throw new Error(e);
     }
@@ -186,7 +196,7 @@ public class TerminologyCache {
     JsonParser json = new JsonParser();
     json.setOutputStyle(OutputStyle.PRETTY);
     try {
-      ct.request = "{\"hierarchical\" : "+(heirarchical ? "true" : "false")+", \"valueSet\" :"+json.composeString(vsc)+"}\r\n";
+      ct.request = "{\"hierarchical\" : "+(heirarchical ? "true" : "false")+", \"valueSet\" :"+extracted(json, vsc)+"}\r\n";
     } catch (IOException e) {
       throw new Error(e);
     }
diff --git a/org.hl7.fhir.validation/src/main/java/org/hl7/fhir/validation/ValidationEngine.java b/org.hl7.fhir.validation/src/main/java/org/hl7/fhir/validation/ValidationEngine.java
index 6eed37701..9375ada7b 100644
--- a/org.hl7.fhir.validation/src/main/java/org/hl7/fhir/validation/ValidationEngine.java
+++ b/org.hl7.fhir.validation/src/main/java/org/hl7/fhir/validation/ValidationEngine.java
@@ -722,7 +722,11 @@ public class ValidationEngine implements IValidatorResourceFetcher, IPackageInst
       return true;
     }
     if (fetcher != null) {
-      return fetcher.resolveURL(appContext, path, url, type);
+      try {
+        return fetcher.resolveURL(appContext, path, url, type);
+      } catch (Exception e) {
+        return false;
+      }
     }
     return false;
   }
diff --git a/org.hl7.fhir.validation/src/main/java/org/hl7/fhir/validation/cli/services/StandAloneValidatorFetcher.java b/org.hl7.fhir.validation/src/main/java/org/hl7/fhir/validation/cli/services/StandAloneValidatorFetcher.java
index 253e0403a..716ed4896 100644
--- a/org.hl7.fhir.validation/src/main/java/org/hl7/fhir/validation/cli/services/StandAloneValidatorFetcher.java
+++ b/org.hl7.fhir.validation/src/main/java/org/hl7/fhir/validation/cli/services/StandAloneValidatorFetcher.java
@@ -21,8 +21,10 @@ import java.io.IOException;
 import java.net.MalformedURLException;
 import java.net.URISyntaxException;
 import java.util.ArrayList;
+import java.util.HashMap;
 import java.util.List;
 import java.util.Locale;
+import java.util.Map;
 
 public class StandAloneValidatorFetcher implements IValidatorResourceFetcher {
 
@@ -30,6 +32,9 @@ public class StandAloneValidatorFetcher implements IValidatorResourceFetcher {
   private FilesystemPackageCacheManager pcm;
   private IWorkerContext context;
   private IPackageInstaller installer;
+  private Map<String, Boolean> urlList = new HashMap<>();
+  private Map<String, String> pidList = new HashMap<>();
+  private Map<String, NpmPackage> pidMap = new HashMap<>();
 
   public StandAloneValidatorFetcher(FilesystemPackageCacheManager pcm, IWorkerContext context, IPackageInstaller installer) {
     super();
@@ -70,15 +75,25 @@ public class StandAloneValidatorFetcher implements IValidatorResourceFetcher {
       return !url.startsWith("http://hl7.org/fhir") && !type.equals("canonical");
     }
 
+    // the next operations are expensive. we're going to cache them 
+    if (urlList.containsKey(url)) {
+      return urlList.get(url);
+    }
     if (base.equals("http://terminology.hl7.org")) {
       pid = "hl7.terminology";
     } else if (url.startsWith("http://hl7.org/fhir")) {
       pid = pcm.getPackageId(base);
     } else {
-      pid = pcm.findCanonicalInLocalCache(base);
+      if (pidList.containsKey(base)) {
+        pid = pidList.get(base);
+      } else {
+        pid = pcm.findCanonicalInLocalCache(base);
+        pidList.put(base, pid);
+      }
     }
     ver = url.contains("|") ? url.substring(url.indexOf("|") + 1) : null;
     if (pid == null && Utilities.startsWithInList(url, "http://hl7.org/fhir", "http://terminology.hl7.org")) {
+      urlList.put(url, false);
       return false;
     }
 
@@ -87,15 +102,32 @@ public class StandAloneValidatorFetcher implements IValidatorResourceFetcher {
       VersionURLInfo vu = VersionUtilities.parseVersionUrl(url);
       if (vu != null) {
         NpmPackage pi = pcm.loadPackage(VersionUtilities.packageForVersion(vu.getVersion()), VersionUtilities.getCurrentVersion(vu.getVersion()));
-        return pi.hasCanonical(vu.getUrl());
+        boolean res = pi.hasCanonical(vu.getUrl());
+        urlList.put(url, res);
+        return res;
       }
     }
 
     // ok maybe it's a reference to a package we know
     if (pid != null) {
-      if (installer.packageExists(pid, ver)) {
-        installer.loadPackage(pid, ver);
-        NpmPackage pi = pcm.loadPackage(pid);
+      if ("sharedhealth.fhir.ca.common".equals(pid)) { // special case - optimise this
+        return false;
+      }
+      NpmPackage pi = null;
+      if (pidMap.containsKey(pid+"|"+ver)) {
+        pi = pidMap.get(pid+"|"+ver);
+      } else  if (installer.packageExists(pid, ver)) {
+        try {
+          installer.loadPackage(pid, ver);
+          pi = pcm.loadPackage(pid);
+          pidMap.put(pid+"|"+ver, pi);
+        } catch (Exception e) {
+          pidMap.put(pid+"|"+ver, null);          
+        }
+      } else {
+        pidMap.put(pid+"|"+ver, null);
+      }
+      if (pi != null) {
         return pi.hasCanonical(url);
       }
     }