diff --git a/R/class_builder.R b/R/class_builder.R
index c82dccc3..ab801026 100644
--- a/R/class_builder.R
+++ b/R/class_builder.R
@@ -27,7 +27,7 @@ target_update_depend.tar_builder <- function(target, pipeline, meta) {
   lookup_set(
     lookup = .subset2(meta, "depends"),
     names = target_get_name(target),
-    value = .subset2(meta, "produce_depend")(target, pipeline)
+    object = .subset2(meta, "produce_depend")(target, pipeline)
   )
 }
 
diff --git a/R/class_database.R b/R/class_database.R
index 2814b68e..724f9b64 100644
--- a/R/class_database.R
+++ b/R/class_database.R
@@ -111,7 +111,7 @@ database_class <- R6::R6Class(
       lookup_set(
         .subset2(self, "lookup"),
         name = as.character(.subset2(row, "name")),
-        value = as.list(row)
+        object = as.list(row)
       )
     },
     del_rows = function(names) {
diff --git a/R/class_future.R b/R/class_future.R
index 3f60401e..a7866755 100644
--- a/R/class_future.R
+++ b/R/class_future.R
@@ -88,7 +88,7 @@ future_class <- R6::R6Class(
         envir = envir
       )
       self$workers <- workers
-      self$worker_list <- memory_init()
+      self$worker_list <- lookup_new()
     },
     run_worker = function(target) {
       builder_marshal_subpipeline(target)
@@ -132,8 +132,8 @@ future_class <- R6::R6Class(
         seed = FALSE
       )
       future <- do.call(what = future::future, args = args)
-      memory_set_object(
-        self$worker_list,
+      lookup_set(
+        lookup = self$worker_list,
         name = target_get_name(target),
         object = future
       )
@@ -179,7 +179,7 @@ future_class <- R6::R6Class(
       self$scheduler$backoff$reset()
     },
     can_submit = function() {
-      self$worker_list$count < self$workers &&
+      lookup_count(self$worker_list) < self$workers &&
         self$scheduler$queue$is_nonempty()
     },
     try_submit = function(wait) {
@@ -193,16 +193,16 @@ future_class <- R6::R6Class(
       tryCatch(future::value(worker, signal = FALSE), error = identity)
     },
     process_worker = function(name) {
-      worker <- memory_get_object(self$worker_list, name)
+      worker <- lookup_get(self$worker_list, name)
       if (future::resolved(worker)) {
         value <- self$future_value(worker)
         self$conclude_worker_target(value, name)
-        memory_del_objects(self$worker_list, name)
+        lookup_remove(self$worker_list, name)
       }
       self$try_submit(wait = FALSE)
     },
     process_workers = function() {
-      names <- self$worker_list$names
+      names <- lookup_list(self$worker_list)
       if (!length(names)) {
         return()
       }
diff --git a/R/class_lookup.R b/R/class_lookup.R
index a8c93663..663203b0 100644
--- a/R/class_lookup.R
+++ b/R/class_lookup.R
@@ -18,9 +18,13 @@ lookup_list <- function(lookup) {
   as.character(names(lookup))
 }
 
-lookup_set <- function(lookup, names, value) {
+lookup_count <- function(lookup) {
+  length(lookup_list(lookup))
+}
+
+lookup_set <- function(lookup, names, object) {
   for (name in names) {
-    lookup[[name]] <- value
+    lookup[[name]] <- object
   }
 }
 
diff --git a/R/class_meta.R b/R/class_meta.R
index 6ef8e84e..769f74e5 100644
--- a/R/class_meta.R
+++ b/R/class_meta.R
@@ -125,7 +125,7 @@ meta_class <- R6::R6Class(
       tar_runtime$meta <- self
     },
     ensure_preprocessed = function(write = FALSE) {
-      if (length(lookup_list(self$database$lookup)) == 0L) {
+      if (lookup_count(self$database$lookup) < 1L) {
         self$preprocess(write = write)
       }
     },
@@ -134,7 +134,11 @@ meta_class <- R6::R6Class(
       hashes <- split(x = data$data, f = data$repository)
       lookup_table <- lookup_new()
       for (name in names(hashes)) {
-        lookup_set(lookup_table, names = name, value = .subset2(hashes, name))
+        lookup_set(
+          lookup = lookup_table,
+          names = name,
+          object = .subset2(hashes, name)
+        )
       }
       self$repository_cas_lookup_table <- lookup_table
     },
diff --git a/R/class_pattern.R b/R/class_pattern.R
index 5057dac0..8df56566 100644
--- a/R/class_pattern.R
+++ b/R/class_pattern.R
@@ -120,7 +120,7 @@ target_update_depend.tar_pattern <- function(target, pipeline, meta) {
   lookup_set(
     lookup = .subset2(meta, "depends"),
     names = target_get_name(target),
-    value = hash_null
+    object = hash_null
   )
 }
 
diff --git a/R/class_store_repository_cas.R b/R/class_store_repository_cas.R
index 31965cc8..31f3beb7 100644
--- a/R/class_store_repository_cas.R
+++ b/R/class_store_repository_cas.R
@@ -71,12 +71,12 @@ store_has_correct_hash.tar_repository_cas <- function(store, file) {
   lookup <- tar_repository_cas_lookup(store)
   key <- .subset2(file, "hash")
   if (lookup_missing(lookup = lookup, name = key)) {
-    value <- store_repository_cas_call_method(
+    object <- store_repository_cas_call_method(
       store = store,
       text = store$methods_repository$exists,
       args = list(key = key)
     )
-    lookup_set(lookup = lookup, names = key, value = value)
+    lookup_set(lookup = lookup, names = key, object = object)
   }
   lookup_get(lookup = lookup, name = key)
 }
@@ -122,9 +122,9 @@ tar_repository_cas_lookup <- function(store) {
     args = list(keys = keys_meta)
   )
   lookup <- lookup_new()
-  lookup_set(lookup, names = as.character(keys_cas), value = TRUE)
-  lookup_set(lookup, names = setdiff(keys_meta, keys_cas), value = FALSE)
-  lookup_set(lookup_table, names = repository, value = lookup)
+  lookup_set(lookup, names = as.character(keys_cas), object = TRUE)
+  lookup_set(lookup, names = setdiff(keys_meta, keys_cas), object = FALSE)
+  lookup_set(lookup_table, names = repository, object = lookup)
   lookup
 }
 
diff --git a/tests/testthat/test-class_future.R b/tests/testthat/test-class_future.R
index 17096505..ad190ee4 100644
--- a/tests/testthat/test-class_future.R
+++ b/tests/testthat/test-class_future.R
@@ -151,7 +151,7 @@ tar_test("branching plan", {
   pipeline <- pipeline_map()
   out <- future_init(pipeline, workers = 2L)
   out$run()
-  expect_equal(out$worker_list$count, 0L)
+  expect_equal(lookup_count(out$worker_list), 0L)
   skipped <- names(out$scheduler$progress$skipped$envir)
   expect_equal(skipped, character(0))
   out2 <- future_init(pipeline_map(), workers = 2L)
diff --git a/tests/testthat/test-class_lookup.R b/tests/testthat/test-class_lookup.R
index ddaa60e1..58d503cc 100644
--- a/tests/testthat/test-class_lookup.R
+++ b/tests/testthat/test-class_lookup.R
@@ -1,7 +1,9 @@
 tar_test("class lookup", {
   lookup <- lookup_new()
-  lookup_set(lookup, names = letters, value = TRUE)
-  lookup_set(lookup, names = LETTERS, value = FALSE)
+  expect_equal(lookup_count(lookup), 0L)
+  lookup_set(lookup, names = letters, object = TRUE)
+  lookup_set(lookup, names = LETTERS, object = FALSE)
+  expect_equal(lookup_count(lookup), length(letters) + length(LETTERS))
   expect_equal(sort(lookup_list(lookup)), sort(c(letters, LETTERS)))
   for (x in letters) {
     expect_true(lookup_exists(lookup, x))
@@ -26,7 +28,7 @@ tar_test("class lookup", {
 
 tar_test("class lookup remove method", {
   lookup <- lookup_new()
-  lookup_set(lookup, names = letters, value = TRUE)
+  lookup_set(lookup, names = letters, object = TRUE)
   expect_equal(sort(lookup_list(lookup)), sort(letters))
   lookup_remove(lookup, letters)
   expect_equal(lookup_list(lookup), character(0L))