diff --git a/README.md b/README.md
index da366ce..cb8eb20 100644
--- a/README.md
+++ b/README.md
@@ -23,6 +23,9 @@
 - [AWS Policy as code OPA](https://github.com/ik-infrastructure-testing/aws-infra-policy-as-code-with-terraform-fork)
 - [Teraform rego](https://developer.hashicorp.com/terraform/cloud-docs/policy-enforcement/define-policies/opa)
 
+
+- [Blog with terraform](https://www.scalr.com/blog/opa-series-part-1-open-policy-agent-and-terraform)
+
 ---
 
 ![](https://img.shields.io/github/commit-activity/m/ik-learning/opa-learn)
diff --git a/playground/ex28/input.json b/playground/ex28/input.json
new file mode 100644
index 0000000..033067f
--- /dev/null
+++ b/playground/ex28/input.json
@@ -0,0 +1,13 @@
+{
+  "attributes": {
+    "request": {
+      "http": {
+        "method": "GET",
+        "path": "/people/",
+        "headers": {
+          "authorization": "Bearer eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJyb2xlIjoiZ3Vlc3QiLCJzdWIiOiJZV3hwWTJVPSIsIm5iZiI6MTUxNDg1MTEzOSwiZXhwIjoxNjQxMDgxNTM5fQ.K5DnnbbIOspRbpCr2IKXE9cPVatGOCBrBQobQmBmaeU"
+        }
+      }
+    }
+  }
+}
diff --git a/playground/ex28/policy.rego b/playground/ex28/policy.rego
new file mode 100644
index 0000000..ef539fc
--- /dev/null
+++ b/playground/ex28/policy.rego
@@ -0,0 +1,43 @@
+package envoy.authz
+
+# https://www.openpolicyagent.org/docs/latest/envoy-primer/
+
+import input.attributes.request.http
+
+default allow := false
+
+allow if {
+	is_token_valid
+	action_allowed
+}
+
+is_token_valid if {
+	token.valid
+	now := time.now_ns() / 1000000000
+	token.payload.nbf <= now
+	now < token.payload.exp
+}
+
+action_allowed if {
+	http.method == "GET"
+	token.payload.role == "guest"
+	glob.match("/people/*", ["/"], http.path)
+}
+
+action_allowed if {
+	http.method == "GET"
+	token.payload.role == "admin"
+	glob.match("/people/*", ["/"], http.path)
+}
+
+action_allowed if {
+	http.method == "POST"
+	token.payload.role == "admin"
+	glob.match("/people", ["/"], http.path)
+	lower(input.parsed_body.firstname) != base64url.decode(token.payload.sub)
+}
+
+token := {"valid": valid, "payload": payload} if {
+	[_, encoded] := split(http.headers.authorization, " ")
+	[valid, _, payload] := io.jwt.decode_verify(encoded, {"secret": "secret"})
+}
diff --git a/playground/ex29/policy.rego b/playground/ex29/policy.rego
new file mode 100644
index 0000000..907324c
--- /dev/null
+++ b/playground/ex29/policy.rego
@@ -0,0 +1,71 @@
+package terraform.module
+
+deny contains msg if {
+	desc := resources[r].values.description
+	contains(desc, "HTTP")
+	msg := sprintf("No security groups should be using HTTP. Resource in violation: %v", [r.address])
+}
+
+resources := {r |
+	some path, value
+
+	# Walk over the JSON tree and check if the node we are
+	# currently on is a module (either root or child) resources
+	# value.
+	walk(input.planned_values, [path, value])
+
+	# Look for resources in the current value based on path
+	rs := module_resources(path, value)
+
+	# Aggregate them into `resources`
+	r := rs[_]
+}
+
+# Variant to match root_module resources
+module_resources(path, value) := rs if {
+	# Expect something like:
+	#
+	#     {
+	#     	"root_module": {
+	#         	"resources": [...],
+	#             ...
+	#         }
+	#         ...
+	#     }
+	#
+	# Where the path is [..., "root_module", "resources"]
+
+	reverse_index(path, 1) == "resources"
+	reverse_index(path, 2) == "root_module"
+	rs := value
+}
+
+# Variant to match child_modules resources
+module_resources(path, value) := rs if {
+	# Expect something like:
+	#
+	#     {
+	#     	...
+	#         "child_modules": [
+	#         	{
+	#             	"resources": [...],
+	#                 ...
+	#             },
+	#             ...
+	#         ]
+	#         ...
+	#     }
+	#
+	# Where the path is [..., "child_modules", 0, "resources"]
+	# Note that there will always be an index int between `child_modules`
+	# and `resources`. We know that walk will only visit each one once,
+	# so we shouldn't need to keep track of what the index is.
+
+	reverse_index(path, 1) == "resources"
+	reverse_index(path, 3) == "child_modules"
+	rs := value
+}
+
+reverse_index(path, idx) := value if {
+	value := path[count(path) - idx]
+}