diff --git a/guix-data-service/database.scm b/guix-data-service/database.scm
index 8c43273..e68f3f1 100644
--- a/guix-data-service/database.scm
+++ b/guix-data-service/database.scm
@@ -22,6 +22,7 @@
   #:use-module (ice-9 exceptions)
   #:use-module (squee)
   #:use-module (prometheus)
+  #:use-module (knots)
   #:use-module (guix-data-service config)
   #:export (get-database-config
             %database-metrics-registry
@@ -226,17 +227,31 @@
           (lambda ()
             (exec-query conn "ROLLBACK;"))
           #:unwind? #t)
-        ;; TODO Include the stack in the exception via knots
         (raise-exception exn))
     (lambda ()
-      (let ((result
-             (parameterize
-                 ((%postgresql-in-transaction? #t))
-               (f conn))))
-        (exec-query conn (if always-rollback?
-                             "ROLLBACK;"
-                             "COMMIT;"))
-        result))
+      (with-exception-handler
+          (lambda (exn)
+            (let ((stack
+                   (match (fluid-ref %stacks)
+                     ((stack-tag . prompt-tag)
+                      (make-stack #t
+                                  0 prompt-tag
+                                  0 (and prompt-tag 1)))
+                     (_
+                      (make-stack #t)))))
+              (raise-exception
+               (make-exception
+                exn
+                (make-knots-exception stack)))))
+        (lambda ()
+          (let ((result
+                 (parameterize
+                     ((%postgresql-in-transaction? #t))
+                   (f conn))))
+            (exec-query conn (if always-rollback?
+                                 "ROLLBACK;"
+                                 "COMMIT;"))
+            result))))
     #:unwind? #t))
 
 (define (check-test-database! conn)
diff --git a/guix-data-service/jobs/load-new-guix-revision.scm b/guix-data-service/jobs/load-new-guix-revision.scm
index 6663a95..9014f09 100644
--- a/guix-data-service/jobs/load-new-guix-revision.scm
+++ b/guix-data-service/jobs/load-new-guix-revision.scm
@@ -177,9 +177,13 @@
       inf)))
    string<?))
 
-(define (all-inferior-system-tests inf store guix-source guix-commit)
+(define* (all-inferior-system-tests inf store guix-source guix-commit
+                                    #:key (ignore-systems '()))
   (define inf-systems
-    (inferior-guix-systems inf))
+    (lset-difference
+     string=?
+     (inferior-guix-systems inf)
+     ignore-systems))
 
   (define extract
     `(lambda (store)
@@ -1304,9 +1308,8 @@ SELECT 1 FROM derivation_source_file_nars WHERE derivation_source_file_id = $1"
               (lambda (conn)
                 (let ((drv (read-derivation-from-file file-name))
                       (postgresql-connection-pool
-                       (make-resource-pool
-                        (const conn)
-                        1
+                       (make-fixed-size-resource-pool
+                        (list conn)
                         #:name "postgres"))
                       (call-with-utility-thread
                        (lambda (thunk)
@@ -1346,10 +1349,13 @@ SELECT 1 FROM derivation_source_file_nars WHERE derivation_source_file_id = $1"
                                1000
                                input-derivations)))))
 
-                       (fix-derivation-inputs conn drv))))))))))
+                       (fix-derivation-inputs conn drv))))
+
+                  (destroy-resource-pool postgresql-connection-pool)))))))
        #:unwind? #t))
    #:hz 0
-   #:parallelism 1))
+   #:parallelism 1
+   #:drain? #t))
 
 (define (fix-derivation-source-file-nar id)
   (run-fibers
@@ -1358,9 +1364,8 @@ SELECT 1 FROM derivation_source_file_nars WHERE derivation_source_file_id = $1"
       "fix"
       (lambda (conn)
         (let ((postgresql-connection-pool
-               (make-resource-pool
-                (const conn)
-                1
+               (make-fixed-size-resource-pool
+                (list conn)
                 #:name "postgres")))
           (match (exec-query
                   conn
@@ -1371,13 +1376,16 @@ SELECT store_path FROM derivation_source_files WHERE id = $1"
              (compute-and-update-derivation-source-file-nar
               postgresql-connection-pool
               id
-              store-path)))))))
+              store-path)))
+
+          (destroy-resource-pool postgresql-connection-pool)))))
    #:hz 0
-   #:parallelism 1))
+   #:parallelism 1
+   #:drain? #t))
 
 (define* (derivation-file-names->derivation-ids postgresql-connection-pool
                                                 call-with-utility-thread
-                                                read-derivations/fiberized
+                                                read-derivations/serialised
                                                 derivation-ids-hash-table
                                                 derivation-file-names
                                                 #:key (log-tag "unspecified"))
@@ -1414,7 +1422,7 @@ SELECT store_path FROM derivation_source_files WHERE id = $1"
             (chunk-for-each!
              (lambda (missing-derivation-file-names-chunk)
                (let ((missing-derivations-chunk
-                      (read-derivations/fiberized
+                      (read-derivations/serialised
                        missing-derivation-file-names-chunk)))
                  (simple-format
                   #t "debug: derivation-file-names->derivation-ids: processing chunk ~A (~A)\n"
@@ -1752,6 +1760,8 @@ SELECT store_path FROM derivation_source_files WHERE id = $1"
                     #:unwind? #t)))))
            systems)))
 
+    (destroy-resource-pool inferior-and-store-pool)
+
     (cons
      (channel-instance-checkout channel-instance)
      result)))
@@ -1972,7 +1982,7 @@ SELECT store_path FROM derivation_source_files WHERE id = $1"
                                    guix-source store-item
                                    guix-derivation
                                    call-with-utility-thread
-                                   read-derivations/fiberized
+                                   read-derivations/serialised
                                    derivation-ids-hash-table
                                    #:key skip-system-tests?
                                    extra-inferior-environment-variables
@@ -2268,43 +2278,50 @@ SELECT store_path FROM derivation_source_files WHERE id = $1"
 
       *unspecified*)
 
+    (define get-derivations/parallelism-limiter
+      (make-parallelism-limiter parallelism))
     (define (get-derivations system target)
-      (let ((derivations-vector (make-vector packages-count)))
-        (with-time-logging
-            (simple-format #f "getting derivations for ~A" (cons system target))
-          (let loop ((start-index 0))
-            (let* ((last-chunk?
-                    (>= (+ start-index chunk-size) packages-count))
-                   (count
-                    (if last-chunk?
-                        (- packages-count start-index)
-                        chunk-size))
-                   (chunk
-                    (call-with-inferior
-                     (lambda (inferior inferior-store)
-                       (ensure-gds-inferior-packages-defined! inferior)
+      ;; Limit concurrency here to keep focused on specific systems until
+      ;; they've been fully processed
+      (with-parallelism-limiter
+       get-derivations/parallelism-limiter
+       (let ((derivations-vector (make-vector packages-count)))
+         (with-time-logging
+             (simple-format #f "getting derivations for ~A"
+                            (cons system target))
+           (let loop ((start-index 0))
+             (let* ((last-chunk?
+                     (>= (+ start-index chunk-size) packages-count))
+                    (count
+                     (if last-chunk?
+                         (- packages-count start-index)
+                         chunk-size))
+                    (chunk
+                     (call-with-inferior
+                      (lambda (inferior inferior-store)
+                        (ensure-gds-inferior-packages-defined! inferior)
 
-                       (let ((result
-                              (inferior-package-derivations
-                               inferior-store
-                               inferior
-                               system
-                               target
-                               start-index
-                               count)))
+                        (let ((result
+                               (inferior-package-derivations
+                                inferior-store
+                                inferior
+                                system
+                                target
+                                start-index
+                                count)))
 
-                         (when last-chunk?
-                           (inferior-cleanup inferior))
+                          (when last-chunk?
+                            (inferior-cleanup inferior))
 
-                         result)))))
-              (vector-copy! derivations-vector
-                            start-index
-                            chunk)
-              (unless last-chunk?
-                (loop (+ start-index chunk-size))))))
-        derivations-vector))
+                          result)))))
+               (vector-copy! derivations-vector
+                             start-index
+                             chunk)
+               (unless last-chunk?
+                 (loop (+ start-index chunk-size))))))
+         derivations-vector)))
 
-    (define (process-system-and-target system target get-derivations)
+    (define (process-system-and-target system target)
       (with-time-logging
           (simple-format #f "processing derivations for ~A" (cons system target))
         (let* ((derivations-vector (get-derivations system target))
@@ -2315,7 +2332,7 @@ SELECT store_path FROM derivation_source_files WHERE id = $1"
                   (derivation-file-names->derivation-ids
                    postgresql-connection-pool
                    call-with-utility-thread
-                   read-derivations/fiberized
+                   read-derivations/serialised
                    derivation-ids-hash-table
                    derivations-vector
                    #:log-tag (simple-format #f "~A:~A" system target))))
@@ -2345,46 +2362,43 @@ SELECT store_path FROM derivation_source_files WHERE id = $1"
 
       'finished)
 
-    (let ((get-derivations/fiberized
-           (fiberize get-derivations
-                     ;; Limit concurrency here to keep focused on specific
-                     ;; systems until they've been fully processed
-                     #:parallelism parallelism)))
-      (with-time-logging "extract-and-store-package-derivations"
-        (fibers-map-with-progress
-         (match-lambda
-           ((system . target)
-            (retry-on-missing-store-item
-             (lambda ()
-               (process-system-and-target system target
-                                          get-derivations/fiberized)))))
-         (list
-          (let ((all-system-target-pairs
-                 (call-with-inferior
-                  (lambda (inferior inferior-store)
-                    (inferior-fetch-system-target-pairs inferior)))))
-            (filter
-             (match-lambda
-               ((system . target)
-                (if (or (member system ignore-systems)
-                        (member target ignore-targets))
-                    (begin
-                      (simple-format
-                       (current-error-port)
-                       "ignoring ~A ~A for package derivations\n"
-                       system
-                       target)
-                      #f)
-                    #t)))
-             all-system-target-pairs)))
-         #:report
-         (lambda (data)
-           (for-each
-            (match-lambda
-              ((result (system . target))
-               (simple-format #t "~A ~A: ~A\n"
-                              system target result)))
-            data))))))
+    (with-time-logging "extract-and-store-package-derivations"
+      (fibers-map-with-progress
+       (match-lambda
+         ((system . target)
+          (retry-on-missing-store-item
+           (lambda ()
+             (process-system-and-target system target)))))
+       (list
+        (let ((all-system-target-pairs
+               (call-with-inferior
+                (lambda (inferior inferior-store)
+                  (inferior-fetch-system-target-pairs inferior)))))
+          (filter
+           (match-lambda
+             ((system . target)
+              (if (or (member system ignore-systems)
+                      (member target ignore-targets))
+                  (begin
+                    (simple-format
+                     (current-error-port)
+                     "ignoring ~A ~A for package derivations\n"
+                     system
+                     target)
+                    #f)
+                  #t)))
+           all-system-target-pairs)))
+       #:report
+       (lambda (data)
+         (for-each
+          (match-lambda
+            ((result (system . target))
+             (simple-format #t "~A ~A: ~A\n"
+                            system target result)))
+          data)))
+      (destroy-parallelism-limiter
+       get-derivations/parallelism-limiter)
+      #t))
 
   (define (extract-and-store-system-tests)
     (if skip-system-tests?
@@ -2400,7 +2414,8 @@ SELECT store_path FROM derivation_source_files WHERE id = $1"
                        inferior
                        inferior-store
                        guix-source
-                       commit))))))
+                       commit
+                       #:ignore-systems ignore-systems))))))
             (when data-with-derivation-file-names
               (let ((data-with-derivation-ids
                      (map (match-lambda
@@ -2414,7 +2429,7 @@ SELECT store_path FROM derivation_source_files WHERE id = $1"
                                            (derivation-file-names->derivation-ids
                                             postgresql-connection-pool
                                             call-with-utility-thread
-                                            read-derivations/fiberized
+                                            read-derivations/serialised
                                             derivation-ids-hash-table
                                             (list->vector
                                              (map cdr derivation-file-names-by-system))
@@ -2439,12 +2454,15 @@ SELECT store_path FROM derivation_source_files WHERE id = $1"
      (with-time-logging "extract-and-store-lint-checkers-and-warnings"
        (extract-and-store-lint-checkers-and-warnings))))
 
+  (destroy-resource-pool inf-and-store-pool)
+  (destroy-resource-pool postgresql-connection-pool)
+
   #t)
 
 (prevent-inlining-for-tests extract-information-from)
 
 (define (load-channel-instances call-with-utility-thread
-                                read-derivations/fiberized
+                                read-derivations/serialised
                                 derivation-ids-hash-table
                                 git-repository-id commit
                                 channel-derivations-by-system)
@@ -2473,9 +2491,8 @@ SELECT store_path FROM derivation_source_files WHERE id = $1"
                     (insert-guix-revision channel-instances-conn
                                           git-repository-id commit)))
                (postgresql-connection-pool
-                (make-resource-pool
-                 (const channel-instances-conn)
-                 1
+                (make-fixed-size-resource-pool
+                 (list channel-instances-conn)
                  #:name "postgres")))
 
           (unless existing-guix-revision-id
@@ -2493,7 +2510,7 @@ SELECT store_path FROM derivation_source_files WHERE id = $1"
                     (derivation-file-names->derivation-ids
                      postgresql-connection-pool
                      call-with-utility-thread
-                     read-derivations/fiberized
+                     read-derivations/serialised
                      derivation-ids-hash-table
                      (list->vector (map cdr derivations-by-system)))))
 
@@ -2537,11 +2554,13 @@ SELECT store_path FROM derivation_source_files WHERE id = $1"
                    (make-missing-store-item-error
                     filename))))
             filenames))))
-  (define read-derivations/fiberized
-    (fiberize read-derivations
-              ;; Don't do this in parallel as there's caching involved with
-              ;; read-derivation-from-file
-              #:parallelism 1))
+
+  (define read-derivations/parallelism-limiter
+    (make-parallelism-limiter 1))
+  (define (read-derivations/serialised . args)
+    (with-parallelism-limiter
+     read-derivations/parallelism-limiter
+     (apply read-derivations args)))
 
   (define derivation-ids-hash-table
     (make-hash-table))
@@ -2581,7 +2600,7 @@ SELECT store_path FROM derivation_source_files WHERE id = $1"
                      channel-derivations-by-system
                      (fibers-force channel-derivations-by-system-promise)))
                 (load-channel-instances call-with-utility-thread
-                                        read-derivations/fiberized
+                                        read-derivations/serialised
                                         derivation-ids-hash-table
                                         git-repository-id commit
                                         channel-derivations-by-system)))
@@ -2608,7 +2627,7 @@ SELECT store_path FROM derivation_source_files WHERE id = $1"
                                      commit guix-source store-item
                                      guix-derivation
                                      call-with-utility-thread
-                                     read-derivations/fiberized
+                                     read-derivations/serialised
                                      derivation-ids-hash-table
                                      #:skip-system-tests?
                                      skip-system-tests?
@@ -2619,6 +2638,9 @@ SELECT store_path FROM derivation_source_files WHERE id = $1"
                                      #:parallelism parallelism)
            (let ((guix-revision-id
                   (fibers-force guix-revision-id-promise)))
+             (destroy-parallelism-limiter
+              read-derivations/parallelism-limiter)
+
              (and
               (if (defined? 'channel-news-for-commit
                     (resolve-module '(guix channels)))
@@ -3133,7 +3155,9 @@ SKIP LOCKED")
                         #:parallelism parallelism))
 
                      (record-job-succeeded conn id)
-                     (record-job-event conn id "success"))
+                     (record-job-event conn id "success")
+
+                     #t)
                     (()
                      (raise-exception
                       job-not-found-exception))))))))
diff --git a/guix-dev.scm b/guix-dev.scm
index b468015..13d1e23 100644
--- a/guix-dev.scm
+++ b/guix-dev.scm
@@ -42,7 +42,7 @@
              (srfi srfi-1))
 
 (define guile-knots
-  (let ((commit "016f37f108ca19da3664516baa97e907aa972b90")
+  (let ((commit "ab5411da423043f2b8a0e27c7507f8d9c34686a2")
         (revision "1"))
     (package
     (name "guile-knots")
@@ -54,7 +54,7 @@
                     (commit commit)))
               (sha256
                (base32
-                "12j3l9p4acf47cjpfzm41ddxyxs1v6vlfa2vrymdd4gdday62xfn"))
+                "0v39yd9cfcwc23cmb4h89kvp9m96xdg47nbj2k80a43fbalfd9aq"))
               (file-name (string-append name "-" version "-checkout"))))
     (build-system gnu-build-system)
     (native-inputs
diff --git a/scripts/guix-data-service-process-job.in b/scripts/guix-data-service-process-job.in
index 5643246..029090d 100644
--- a/scripts/guix-data-service-process-job.in
+++ b/scripts/guix-data-service-process-job.in
@@ -93,18 +93,27 @@
      (with-fluids ((%file-port-name-canonicalization 'none))
        (run-fibers
         (lambda ()
-          (process-load-new-guix-revision-job
-           job
-           #:skip-system-tests? (assq-ref opts 'skip-system-tests)
-           #:extra-inferior-environment-variables
-           (filter-map
-            (match-lambda
-              (('inferior-environment-variable key val)
-               (cons key val))
-              (_ #f))
-            opts)
-           #:ignore-systems (assq-ref opts 'ignore-systems)
-           #:ignore-targets (assq-ref opts 'ignore-targets)
-           #:parallelism (assq-ref opts 'parallelism)))
+          (with-exception-handler
+              (lambda (exn)
+                ;; Exit if exceptions get this far, as not all fibers are
+                ;; guaranteed to finish
+                (primitive-exit 1))
+            (lambda ()
+              (process-load-new-guix-revision-job
+               job
+               #:skip-system-tests? (assq-ref opts 'skip-system-tests)
+               #:extra-inferior-environment-variables
+               (filter-map
+                (match-lambda
+                  (('inferior-environment-variable key val)
+                   (cons key val))
+                  (_ #f))
+                opts)
+               #:ignore-systems (assq-ref opts 'ignore-systems)
+               #:ignore-targets (assq-ref opts 'ignore-targets)
+               #:parallelism (assq-ref opts 'parallelism)))
+            #:unwind? #t))
         #:hz 0
-        #:parallelism 1)))))
+        #:parallelism 1
+        ;; Drain to make sure there are no bugs with the use of fibers
+        #:drain? #t)))))
diff --git a/tests/jobs-load-new-guix-revision.scm b/tests/jobs-load-new-guix-revision.scm
index 64f2464..84d78e8 100644
--- a/tests/jobs-load-new-guix-revision.scm
+++ b/tests/jobs-load-new-guix-revision.scm
@@ -106,7 +106,8 @@
                     (process-load-new-guix-revision-job
                      id #:parallelism 1))
                   #:hz 0
-                  #:parallelism 1))))))))))))))
+                  #:parallelism 1
+                  #:drain? #t))))))))))))))
 
    (exec-query conn "TRUNCATE guix_revisions CASCADE")
    (exec-query conn "TRUNCATE load_new_guix_revision_jobs CASCADE")