diff --git a/lib/gc_index_relay/nostr.ex b/lib/gc_index_relay/nostr.ex
index 1ab2725..b5beb2c 100644
--- a/lib/gc_index_relay/nostr.ex
+++ b/lib/gc_index_relay/nostr.ex
@@ -23,10 +23,13 @@ defmodule GcIndexRelay.Nostr do
   """
   @spec get_event(binary()) :: {:ok, PubEvent.t()} | {:error, :not_found}
   def get_event(id) when is_binary(id) do
-    Event
-    |> Repo.get(id)
-    |> Repo.preload(:tags)
-    |> PubEvent.from_db()
+    with {:ok, binary_id} <- Base.decode16(id, case: :lower),
+         %Event{} = event <- Repo.get(Event, binary_id),
+         event_with_tags <- Repo.preload(event, :tags) do
+      PubEvent.from_db(event_with_tags)
+    else
+      _ -> {:error, :not_found}
+    end
   end
 
   @doc """
@@ -56,9 +59,11 @@ defmodule GcIndexRelay.Nostr do
     with {:ok, event} <- Validator.validate_id(event),
          {:ok, event} <- Validator.validate_signature(event) do
       db_event = PubEvent.to_db(event)
+      tags_as_maps = Enum.map(db_event.tags, &Map.from_struct/1)
+      attrs = db_event |> Map.from_struct() |> Map.put(:tags, tags_as_maps)
 
       %Event{}
-      |> Event.changeset(Map.from_struct(db_event))
+      |> Event.changeset(attrs)
       |> Repo.insert()
     end
   end
@@ -68,10 +73,10 @@ defmodule GcIndexRelay.Nostr do
   """
   @spec delete_event(PubEvent.t()) :: {:ok, Ecto.Schema.t()} | {:error, Ecto.Changeset.t()}
   def delete_event(event) when is_struct(event, PubEvent) do
-    db_event = PubEvent.to_db(event)
-
-    %Event{}
-    |> Event.changeset(Map.from_struct(db_event))
-    |> Repo.delete()
+    with {:ok, binary_id} <- Base.decode16(event.id, case: :lower) do
+      Repo.delete(%Event{id: binary_id})
+    else
+      _ -> {:error, :not_found}
+    end
   end
 end
diff --git a/lib/gc_index_relay/nostr/event.ex b/lib/gc_index_relay/nostr/event.ex
index 934615c..0193451 100644
--- a/lib/gc_index_relay/nostr/event.ex
+++ b/lib/gc_index_relay/nostr/event.ex
@@ -19,7 +19,7 @@ defmodule GcIndexRelay.Nostr.Event do
 
   alias GcIndexRelay.Nostr.Tag
 
-  @primary_key {:id, :binary_id, autogenerate: false}
+  @primary_key {:id, :binary, autogenerate: false}
   schema "events" do
     field :pubkey, :binary
     field :created_at, :utc_datetime
diff --git a/lib/gc_index_relay/nostr/filter.ex b/lib/gc_index_relay/nostr/filter.ex
index 5b6e04a..e64e7ed 100644
--- a/lib/gc_index_relay/nostr/filter.ex
+++ b/lib/gc_index_relay/nostr/filter.ex
@@ -248,12 +248,20 @@ defmodule GcIndexRelay.Nostr.Filter do
   @spec apply_ids(Ecto.Query.t(), [String.t()] | nil) :: Ecto.Query.t()
   defp apply_ids(query, nil), do: query
   defp apply_ids(query, []), do: query
-  defp apply_ids(query, ids), do: where(query, [e], e.id in ^ids)
+
+  defp apply_ids(query, ids) do
+    binary_ids = Enum.map(ids, &Base.decode16!(&1, case: :lower))
+    where(query, [e], e.id in ^binary_ids)
+  end
 
   @spec apply_authors(Ecto.Query.t(), [String.t()] | nil) :: Ecto.Query.t()
   defp apply_authors(query, nil), do: query
   defp apply_authors(query, []), do: query
-  defp apply_authors(query, authors), do: where(query, [e], e.pubkey in ^authors)
+
+  defp apply_authors(query, authors) do
+    binary_authors = Enum.map(authors, &Base.decode16!(&1, case: :lower))
+    where(query, [e], e.pubkey in ^binary_authors)
+  end
 
   @spec apply_kinds(Ecto.Query.t(), [integer()] | nil) :: Ecto.Query.t()
   defp apply_kinds(query, nil), do: query
@@ -262,11 +270,19 @@ defmodule GcIndexRelay.Nostr.Filter do
 
   @spec apply_since(Ecto.Query.t(), integer() | nil) :: Ecto.Query.t()
   defp apply_since(query, nil), do: query
-  defp apply_since(query, since), do: where(query, [e], e.created_at >= ^since)
+
+  defp apply_since(query, since) when is_integer(since) do
+    datetime = DateTime.from_unix!(since)
+    where(query, [e], e.created_at >= ^datetime)
+  end
 
   @spec apply_until(Ecto.Query.t(), integer() | nil) :: Ecto.Query.t()
   defp apply_until(query, nil), do: query
-  defp apply_until(query, until), do: where(query, [e], e.created_at <= ^until)
+
+  defp apply_until(query, until) when is_integer(until) do
+    datetime = DateTime.from_unix!(until)
+    where(query, [e], e.created_at <= ^datetime)
+  end
 
   @spec apply_tags(Ecto.Query.t(), map() | nil) :: Ecto.Query.t()
   defp apply_tags(query, nil), do: query
diff --git a/lib/gc_index_relay/nostr/tag.ex b/lib/gc_index_relay/nostr/tag.ex
index 5501c00..dfaf26c 100644
--- a/lib/gc_index_relay/nostr/tag.ex
+++ b/lib/gc_index_relay/nostr/tag.ex
@@ -6,7 +6,7 @@ defmodule GcIndexRelay.Nostr.Tag do
     field :name, :string
     field :value, :string
     field :additional_values, {:array, :string}
-    belongs_to :event, GcIndexRelay.Nostr.Event
+    belongs_to :event, GcIndexRelay.Nostr.Event, type: :binary
   end
 
   @doc false
diff --git a/lib/gc_index_relay_web/controllers/event_controller.ex b/lib/gc_index_relay_web/controllers/event_controller.ex
index 610e998..bd5670c 100644
--- a/lib/gc_index_relay_web/controllers/event_controller.ex
+++ b/lib/gc_index_relay_web/controllers/event_controller.ex
@@ -20,12 +20,14 @@ defmodule GcIndexRelayWeb.EventController do
   end
 
   def create(conn, %{"event" => event_params}) do
-    # TODO: Add 400 for invalid event in FallbackController
-    with {:ok, %Event{} = event} <- Nostr.create_event(event_params) do
+    atoms_map = Map.new(event_params, fn {k, v} -> {String.to_existing_atom(k), v} end)
+    pub_event = struct(PubEvent, atoms_map)
+
+    with {:ok, _event} <- Nostr.create_event(pub_event) do
       conn
       |> put_status(:created)
-      |> put_resp_header("location", ~p"/api/events/#{event.id}")
-      |> render(:show, event: event)
+      |> put_resp_header("location", ~p"/api/events/#{pub_event.id}")
+      |> render(:show, event: pub_event)
     end
   end
 
@@ -45,9 +47,9 @@ defmodule GcIndexRelayWeb.EventController do
   end
 
   def show(conn, %{"id" => id}) do
-    # TODO: Add 404 for event not found in FallbackController
-    event = Nostr.get_event(id)
-    render(conn, :show, event: event)
+    with {:ok, pub_event} <- Nostr.get_event(id) do
+      render(conn, :show, event: pub_event)
+    end
   end
 
   swagger_path :delete do
diff --git a/lib/gc_index_relay_web/controllers/event_json.ex b/lib/gc_index_relay_web/controllers/event_json.ex
index 4379e4d..5afa408 100644
--- a/lib/gc_index_relay_web/controllers/event_json.ex
+++ b/lib/gc_index_relay_web/controllers/event_json.ex
@@ -1,5 +1,5 @@
 defmodule GcIndexRelayWeb.EventJSON do
-  alias GcIndexRelay.Nostr.Event
+  alias GcIndexRelay.Nostr.PubEvent
 
   @doc """
   Renders a single event.
@@ -8,7 +8,7 @@ defmodule GcIndexRelayWeb.EventJSON do
     %{data: data(event)}
   end
 
-  defp data(%Event{} = event) do
+  defp data(%PubEvent{} = event) do
     %{
       id: event.id,
       pubkey: event.pubkey,
diff --git a/lib/gc_index_relay_web/controllers/fallback_controller.ex b/lib/gc_index_relay_web/controllers/fallback_controller.ex
index 44b8aa8..0738f37 100644
--- a/lib/gc_index_relay_web/controllers/fallback_controller.ex
+++ b/lib/gc_index_relay_web/controllers/fallback_controller.ex
@@ -7,11 +7,18 @@ defmodule GcIndexRelayWeb.FallbackController do
   use GcIndexRelayWeb, :controller
 
   # This clause handles errors returned by Ecto's insert/update/delete.
+  # Returns 409 Conflict for duplicate event IDs, 422 for other changeset errors.
   def call(conn, {:error, %Ecto.Changeset{} = changeset}) do
-    conn
-    |> put_status(:unprocessable_entity)
-    |> put_view(json: GcIndexRelayWeb.ChangesetJSON)
-    |> render(:error, changeset: changeset)
+    if duplicate_id_error?(changeset) do
+      conn
+      |> put_status(:conflict)
+      |> json(%{errors: %{detail: "Event already exists"}})
+    else
+      conn
+      |> put_status(:unprocessable_entity)
+      |> put_view(json: GcIndexRelayWeb.ChangesetJSON)
+      |> render(:error, changeset: changeset)
+    end
   end
 
   # This clause handles string error messages (e.g., from filter validation).
@@ -28,4 +35,11 @@ defmodule GcIndexRelayWeb.FallbackController do
     |> put_view(html: GcIndexRelayWeb.ErrorHTML, json: GcIndexRelayWeb.ErrorJSON)
     |> render(:"404")
   end
+
+  defp duplicate_id_error?(%Ecto.Changeset{errors: errors}) do
+    Enum.any?(errors, fn
+      {:id, {_, opts}} -> Keyword.get(opts, :constraint) == :unique
+      _ -> false
+    end)
+  end
 end
diff --git a/lib/gc_index_relay_web/controllers/filter_controller.ex b/lib/gc_index_relay_web/controllers/filter_controller.ex
index 143afbc..a6a79bc 100644
--- a/lib/gc_index_relay_web/controllers/filter_controller.ex
+++ b/lib/gc_index_relay_web/controllers/filter_controller.ex
@@ -83,7 +83,7 @@ defmodule GcIndexRelayWeb.FilterController do
 
   @spec validate_param_values(map()) :: {:ok, map()} | {:error, String.t()}
   def validate_param_values(params) do
-    %{:limit => limit} = params
+    %{"limit" => limit} = params
 
     if limit < 1 or limit > 100 do
       {:error, "The filter limit must be between 1 and 100."}
@@ -123,7 +123,9 @@ defmodule GcIndexRelayWeb.FilterController do
       params
       |> Map.keys()
       |> Enum.reject(fn key ->
-        key in known_keys or String.starts_with?(key, "#")
+        key in known_keys or String.starts_with?(key, "#") or
+          (byte_size(key) == 1 and
+             ((key >= "a" and key <= "z") or (key >= "A" and key <= "Z")))
       end)
 
     case unknown_keys do
@@ -135,16 +137,22 @@ defmodule GcIndexRelayWeb.FilterController do
   # Parse individual parameters from strings to proper types
   @spec parse_params(map()) :: {:ok, map()} | {:error, String.t()}
   defp parse_params(params) do
-    result =
-      params
-      |> Enum.reduce_while({:ok, %{}}, fn {key, value}, {:ok, acc} ->
-        case parse_param(key, value) do
-          {:ok, parsed_value} -> {:cont, {:ok, Map.put(acc, key, parsed_value)}}
-          {:error, _} = error -> {:halt, error}
-        end
-      end)
-
-    result
+    params
+    |> Enum.reduce_while({:ok, %{}}, fn {key, value}, {:ok, acc} ->
+      case parse_param(key, value) do
+        {:ok, parsed_value} ->
+          out_key =
+            if byte_size(key) == 1 and
+                 ((key >= "a" and key <= "z") or (key >= "A" and key <= "Z")),
+               do: "#" <> key,
+               else: key
+
+          {:cont, {:ok, Map.put(acc, out_key, parsed_value)}}
+
+        {:error, _} = error ->
+          {:halt, error}
+      end
+    end)
   end
 
   # Parse individual parameter based on its key
@@ -183,7 +191,8 @@ defmodule GcIndexRelayWeb.FilterController do
 
   defp parse_param("limit", value) do
     case Integer.parse(value) do
-      {int, ""} -> {:ok, int}
+      {int, ""} when int >= 1 and int <= 100 -> {:ok, int}
+      {int, ""} when is_integer(int) -> {:error, "The limit must be between 1 and 100."}
       _ -> {:error, "Invalid limit value: '#{value}' must be an integer"}
     end
   end
@@ -192,4 +201,10 @@ defmodule GcIndexRelayWeb.FilterController do
   defp parse_param("#" <> _tag_name, value) do
     {:ok, String.split(value, ",")}
   end
+
+  # Handle single-letter tag filters without "#" prefix (e.g., "p" instead of "#p")
+  # The "#" is trimmed by URL fragment parsing; bare single-letter keys are treated as tag filters
+  defp parse_param(<<letter>> = _key, value) when letter in ?a..?z do
+    {:ok, String.split(value, ",")}
+  end
 end
diff --git a/priv/repo/migrations/20260129043804_add_nostr_events.exs b/priv/repo/migrations/20260129043804_add_nostr_events.exs
index ad82ac1..afb5062 100644
--- a/priv/repo/migrations/20260129043804_add_nostr_events.exs
+++ b/priv/repo/migrations/20260129043804_add_nostr_events.exs
@@ -3,7 +3,7 @@ defmodule GcIndexRelay.Repo.Migrations.AddNostrEvents do
 
   def change do
     create table(:events, primary_key: false) do
-      add :id, :binary_id, primary_key: true
+      add :id, :binary, primary_key: true
       add :pubkey, :binary, null: false
       add :created_at, :utc_datetime, null: false
       add :kind, :integer, null: false
@@ -18,7 +18,7 @@ defmodule GcIndexRelay.Repo.Migrations.AddNostrEvents do
       add :name, :string, null: false
       add :value, :string, null: false
       add :additional_values, {:array, :string}
-      add :event_id, references(:events, type: :binary_id, on_delete: :delete_all), null: false
+      add :event_id, references(:events, type: :binary, on_delete: :delete_all), null: false
     end
 
     create index(:tags, [:event_id])
diff --git a/test/gc_index_relay_web/controllers/filter_controller_test.exs b/test/gc_index_relay_web/controllers/filter_controller_test.exs
index 8841bca..d20130e 100644
--- a/test/gc_index_relay_web/controllers/filter_controller_test.exs
+++ b/test/gc_index_relay_web/controllers/filter_controller_test.exs
@@ -73,7 +73,7 @@ defmodule GcIndexRelayWeb.FilterControllerTest do
       {:ok, _} = GcIndexRelay.Nostr.create_event(tagged_pub_event)
       event_fixture(%{kind: 2, created_at: 1_640_000_001})
 
-      conn = get(conn, ~p"/api/events?since=0&until=9999999999&limit=10&#p=abc123def456")
+      conn = get(conn, ~p"/api/events?since=0&until=9999999999&limit=10&p=abc123def456")
 
       assert %{"data" => events} = json_response(conn, 200)
       assert length(events) == 1