diff --git a/polkadot/.gitlab-ci.yml b/polkadot/.gitlab-ci.yml
index 31bea94204..a977ea02a6 100644
--- a/polkadot/.gitlab-ci.yml
+++ b/polkadot/.gitlab-ci.yml
@@ -6,6 +6,7 @@
 
 
 stages:
+  - merge-test
   - test
   - build
   - publish
@@ -24,11 +25,7 @@ variables:
 
 
 
-cache:
-  key:                             "${CI_JOB_NAME}"
-  paths:
-    - ./.cargo/
-
+cache:                             {}
 
 .collect_artifacts:                &collect_artifacts
   artifacts:
@@ -40,17 +37,49 @@ cache:
 
 
 
+.kubernetes_build:                 &kubernetes_build
+  tags:
+    - kubernetes-parity-build
+  environment:
+    name: gke-build
+
+
+
+
 # disabled as there are bugs
 # before_script:
 #   - ./scripts/build.sh
 
 
 
+#### stage:                        merge-test
+
+check:merge:conflict:
+  stage:                           merge-test
+  image:                           parity/tools:latest
+  cache:                           {}
+  <<:                              *kubernetes_build
+  only:
+    - /^[0-9]+$/
+  variables:
+    GITHUB_API:                    "https://api.github.com"
+    GITLAB_API:                    "https://gitlab.parity.io/api/v4"
+    GITHUB_API_PROJECT:            "parity%2Finfrastructure%2Fgithub-api"
+  script:
+    - ./scripts/gitlab/check_merge_conflict.sh
+
+
+
 # test will be run for ci on the current repo
 # for version v0.2 branch tests are located in substrate repository and 
 # therefore not generically testable
 test:rust:release:
   stage:                           test
+  cache:
+    key:                           "${CI_JOB_NAME}-test"
+    paths:
+      - ${CARGO_HOME}
+      - ./target
   only:
     - triggers
     - tags
@@ -71,6 +100,11 @@ test:rust:release:
 
 build:rust:linux:release:
   stage:                           build
+  cache:
+    key:                           "${CI_JOB_NAME}-build"
+    paths:
+      - ${CARGO_HOME}
+      - ./target
   <<:                              *collect_artifacts
   only:
     - master
@@ -146,13 +180,14 @@ dockerize:release:
   when:                            manual
   cache:                           {}
   retry:                           1
-  image: dtzar/helm-kubectl:$HELM_VERSION
+  image:                           dtzar/helm-kubectl:$HELM_VERSION
   only:
     - master
     - tags
     - web
   tags:
-    - kubernetes
+    # this is the runner that is used to deploy it
+    - kubernetes-parity-build
   before_script:
     - test -z "${DEPLOY_TAG}" && 
       test -f ./target/release/VERSION && 
@@ -181,11 +216,11 @@ dockerize:release:
 deploy:ew3:
   <<:                              *deploy
   environment:
-    name: gke-beta-ew3
+    name: parity-prod-ew3
 
 deploy:ue1:
   <<:                              *deploy
   environment:
-    name: gke-beta-ue1
+    name: parity-prod-ue1
 
 
diff --git a/polkadot/scripts/gitlab/check_merge_conflict.sh b/polkadot/scripts/gitlab/check_merge_conflict.sh
new file mode 100755
index 0000000000..8738340e71
--- /dev/null
+++ b/polkadot/scripts/gitlab/check_merge_conflict.sh
@@ -0,0 +1,110 @@
+#!/bin/sh
+#
+# check if there is a merge conflict with this pull request only about wasm 
+# binary blobs. if so trigger a rebuild of it and push it on the feature 
+# branch if owned by paritytech
+#
+
+set -e # fail on any error
+
+NODE_RUNTIME_COMPACT="runtime/wasm/target/wasm32-unknown-unknown/release/polkadot_runtime.compact.wasm"
+NODE_RUNTIME="runtime/wasm/target/wasm32-unknown-unknown/release/polkadot_runtime.wasm"
+
+
+
+jsonfile="$(mktemp)"
+
+attemptno="1"
+while ( ! test -s ${jsonfile} ) \
+	|| ( [ "$(jq -r .mergeable ${jsonfile})" = "null" ] \
+	     && [ "${attemptno}" -lt 5 ] )
+do
+	echo "|  checking pull request status (attempt no ${attemptno})"
+	curl -sS -o ${jsonfile} -H "Accept: application/vnd.github.v3+json" \
+	  "${GITHUB_API}/repos/paritytech/polkadot/pulls/${CI_COMMIT_REF_NAME}"
+	sleep 3
+	attemptno="$(( ${attemptno} + 1 ))"
+done
+
+
+
+baseref="$(jq -r .head.ref ${jsonfile})"
+baserepo="$(jq -r .head.repo.full_name ${jsonfile})"
+mergeable="$(jq -r .mergeable ${jsonfile})"
+
+rm -f ${jsonfile}
+
+
+cat <<-EOT
+|
+|  pr is of feature branch ${baseref} on ${baserepo}
+|
+|  tell me github is this branch mergeable into the master branch?
+|
+EOT
+
+test "${mergeable}" = "true" && echo "|  yes, it is." && exit 0
+
+if [ "${baseref}" = "null" -a "${baserepo}" = "null" ]
+then
+	echo "| either connectivity issues with github or pull request not existant"
+	exit 3
+fi
+
+cat <<-EOT
+|  not mergeable
+|
+|  github sees a conflict - check if it's only about the following wasm blobs
+|
+|	- ${NODE_RUNTIME_COMPACT}
+|	- ${NODE_RUNTIME}
+|
+EOT
+
+git fetch origin master
+git config --global user.email "devops-team+polkadot-ci-merge-conflict@parity.io"
+git config --global user.name "I shall never commit to anything"
+
+cat <<-EOT
+|
+|  trying to merge with the master branch to see if there is a conflict about
+|  the wasm files only
+|
+EOT
+
+if git merge --no-commit --no-ff origin/master | grep '^CONFLICT ' \
+	| grep -v -e ${NODE_RUNTIME_COMPACT} -e ${NODE_RUNTIME}
+then
+  git merge --abort
+	echo "|  there are more conflicting files than the wasm blobs"
+	exit 1
+fi
+git merge --abort
+
+
+cat <<-EOT
+|
+|  only wasm blobs block the merge.
+|
+|  triggering rebuild of wasm blobs which will be pushed onto the feature 
+|  branch of this pull request upon success.
+| 
+|  see:
+|
+EOT
+
+
+
+curl -sS -X POST \
+	-F "token=${CI_JOB_TOKEN}" \
+	-F "ref=master" \
+	-F "variables[REBUILD_WASM]=\"${baserepo}:${baseref}\"" \
+	${GITLAB_API}/projects/${GITHUB_API_PROJECT}/trigger/pipeline \
+	| jq -r .web_url
+
+# fail as there will be another commit on top of that feature branch that will
+# be tested anyway.
+exit 1
+
+
+# vim: noexpandtab