diff --git a/internal/channel/plugin.go b/internal/channel/plugin.go
index 9b0d8caf..54b21cac 100644
--- a/internal/channel/plugin.go
+++ b/internal/channel/plugin.go
@@ -230,5 +230,9 @@ func ValidateType(t string) error {
 		return fmt.Errorf("type contains invalid chars, may only contain a-zA-Z0-9, %q given", t)
 	}
 
+	if len(t) > 255 {
+		return fmt.Errorf("type is too long, at most 255 chars allowed, %d given", len(t))
+	}
+
 	return nil
 }
diff --git a/internal/event/event.go b/internal/event/event.go
index b84843a7..5a258f88 100644
--- a/internal/event/event.go
+++ b/internal/event/event.go
@@ -68,6 +68,20 @@ func (e *Event) Validate() error {
 		return fmt.Errorf("invalid event: tags must not be empty")
 	}
 
+	for tag := range e.Tags {
+		if len(tag) > 255 {
+			return fmt.Errorf("invalid event: tag %q is too long, at most 255 chars allowed, %d given", tag, len(tag))
+		}
+	}
+
+	for tag := range e.ExtraTags {
+		if len(tag) > 255 {
+			return fmt.Errorf(
+				"invalid event: extra tag %q is too long, at most 255 chars allowed, %d given", tag, len(tag),
+			)
+		}
+	}
+
 	if e.SourceId == 0 {
 		return fmt.Errorf("invalid event: source ID must not be empty")
 	}
diff --git a/schema/pgsql/schema.sql b/schema/pgsql/schema.sql
index 4d04dd7e..8b0213ff 100644
--- a/schema/pgsql/schema.sql
+++ b/schema/pgsql/schema.sql
@@ -31,7 +31,7 @@ CREATE OR REPLACE FUNCTION anynonarrayliketext(anynonarray, text)
 CREATE OPERATOR ~~ (LEFTARG=anynonarray, RIGHTARG=text, PROCEDURE=anynonarrayliketext);
 
 CREATE TABLE available_channel_type (
-    type text NOT NULL,
+    type varchar(255) NOT NULL,
     name text NOT NULL,
     version text NOT NULL,
     author text NOT NULL,
@@ -43,7 +43,7 @@ CREATE TABLE available_channel_type (
 CREATE TABLE channel (
     id bigserial,
     name citext NOT NULL,
-    type text NOT NULL, -- 'email', 'sms', ...
+    type varchar(255) NOT NULL, -- 'email', 'sms', ...
     config text, -- JSON with channel-specific attributes
     -- for now type determines the implementation, in the future, this will need a reference to a concrete
     -- implementation to allow multiple implementations of a sms channel for example, probably even user-provided ones
@@ -71,6 +71,7 @@ CREATE TABLE contact (
     -- As the username is unique, it must be NULLed for deletion via "deleted = 'y'"
     CONSTRAINT uk_contact_username UNIQUE (username),
 
+    CONSTRAINT ck_contact_username_up_to_254_chars CHECK (length(username) <= 254),
     CONSTRAINT fk_contact_channel FOREIGN KEY (default_channel_id) REFERENCES channel(id)
 );
 
@@ -79,7 +80,7 @@ CREATE INDEX idx_contact_changed_at ON contact(changed_at);
 CREATE TABLE contact_address (
     id bigserial,
     contact_id bigint NOT NULL,
-    type text NOT NULL, -- 'phone', 'email', ...
+    type varchar(255) NOT NULL, -- 'phone', 'email', ...
     address text NOT NULL, -- phone number, email address, ...
 
     changed_at bigint NOT NULL,
@@ -285,7 +286,7 @@ CREATE TABLE object (
 
 CREATE TABLE object_id_tag (
     object_id bytea NOT NULL,
-    tag text NOT NULL,
+    tag varchar(255) NOT NULL,
     value text NOT NULL,
 
     CONSTRAINT pk_object_id_tag PRIMARY KEY (object_id, tag),
@@ -294,7 +295,7 @@ CREATE TABLE object_id_tag (
 
 CREATE TABLE object_extra_tag (
     object_id bytea NOT NULL,
-    tag text NOT NULL,
+    tag varchar(255) NOT NULL,
     value text NOT NULL,
 
     CONSTRAINT pk_object_extra_tag PRIMARY KEY (object_id, tag),
@@ -495,7 +496,8 @@ CREATE TABLE browser_session (
     user_agent varchar(4096) NOT NULL,
     authenticated_at bigint NOT NULL,
 
-    CONSTRAINT pk_browser_session PRIMARY KEY (php_session_id)
+    CONSTRAINT pk_browser_session PRIMARY KEY (php_session_id),
+    CONSTRAINT ck_browser_session_username_up_to_254_chars CHECK (length(username) <= 254)
 );
 
 CREATE INDEX idx_browser_session_authenticated_at ON browser_session (authenticated_at DESC);
diff --git a/schema/pgsql/upgrades/034.sql b/schema/pgsql/upgrades/034.sql
new file mode 100644
index 00000000..24f9817d
--- /dev/null
+++ b/schema/pgsql/upgrades/034.sql
@@ -0,0 +1,7 @@
+ALTER TABLE available_channel_type ALTER COLUMN type TYPE varchar(255);
+ALTER TABLE channel ALTER COLUMN type TYPE varchar(255);
+ALTER TABLE contact ADD CONSTRAINT ck_contact_username_up_to_254_chars CHECK (length(username) <= 254);
+ALTER TABLE contact_address ALTER COLUMN type TYPE varchar(255);
+ALTER TABLE object_id_tag ALTER COLUMN tag TYPE varchar(255);
+ALTER TABLE object_extra_tag ALTER COLUMN tag TYPE varchar(255);
+ALTER TABLE browser_session ADD CONSTRAINT ck_browser_session_username_up_to_254_chars CHECK (length(username) <= 254);