diff --git a/service/paxos/paxos_state.cc b/service/paxos/paxos_state.cc
index a051230cf3..2da4136e56 100644
--- a/service/paxos/paxos_state.cc
+++ b/service/paxos/paxos_state.cc
@@ -438,9 +438,10 @@ static future<cql3::untyped_result_set> do_execute_cql_with_timeout(sstring req,
 
     const auto cache_key = qp.compute_id(req, "", cql3::internal_dialect());
     auto ps_ptr = qp.get_prepared(cache_key);
+    shared_ptr<cql_transport::messages::result_message::prepared> prepared_msg;
     if (!ps_ptr) {
-        const auto msg_ptr = co_await qp.prepare(req, qs, cql3::internal_dialect());
-        ps_ptr = msg_ptr->get_prepared();
+        prepared_msg = co_await qp.prepare(req, qs, cql3::internal_dialect());
+        ps_ptr = prepared_msg->get_prepared();
         if (!ps_ptr) {
             on_internal_error(paxos_state::logger, "prepared statement is null");
         }
@@ -449,8 +450,8 @@ static future<cql3::untyped_result_set> do_execute_cql_with_timeout(sstring req,
         -1, service::node_local_only::yes);
     const auto st = ps_ptr->statement;
 
-    const auto msg_ptr = co_await st->execute(qp, qs, qo, std::nullopt);
-    co_return cql3::untyped_result_set(msg_ptr);
+    const auto result_ptr = co_await st->execute(qp, qs, qo, std::nullopt);
+    co_return cql3::untyped_result_set(result_ptr);
 }
 
 template <typename... Args>
diff --git a/table_helper.cc b/table_helper.cc
index 8f5a55096e..b96e97c977 100644
--- a/table_helper.cc
+++ b/table_helper.cc
@@ -135,7 +135,23 @@ future<> table_helper::cache_table_info(cql3::query_processor& qp, service::migr
 }
 
 future<> table_helper::insert(cql3::query_processor& qp, service::migration_manager& mm, service::query_state& qs, noncopyable_function<cql3::query_options ()> opt_maker) {
-    co_await cache_table_info(qp, mm, qs);
+    // _prepared_stmt is a checked_weak_ptr into the prepared statements
+    // cache and can be invalidated by a concurrent purge (e.g. on a schema
+    // change). cache_table_info() (re-)prepares and assigns _prepared_stmt,
+    // but the pin protecting the entry is dropped when try_prepare()
+    // returns. In release the chain of ready-future co_awaits back to here
+    // resumes synchronously, but debug builds preempt on every co_await
+    // even for ready futures, opening a window for a purge to drop the
+    // entry and leave _prepared_stmt null. Loop until a synchronous
+    // post-resume check finds _prepared_stmt valid; nothing can run between
+    // that check and the dereference below. _insert_stmt is a strong
+    // shared_ptr and is not affected by cache invalidation.
+    while (true) {
+        co_await cache_table_info(qp, mm, qs);
+        if (_prepared_stmt) {
+            break;
+        }
+    }
     auto opts = opt_maker();
     opts.prepare(_prepared_stmt->bound_names);
     co_await _insert_stmt->execute(qp, qs, opts, std::nullopt);