diff --git a/public_transaction_ids/create_and_use_functions.sql b/public_transaction_ids/create_and_use_functions.sql
new file mode 100644
index 0000000..6a7ca29
--- /dev/null
+++ b/public_transaction_ids/create_and_use_functions.sql
@@ -0,0 +1,155 @@
+-- Base62 encoding, which is reversible
+-- Create to_base62_fixed function
+CREATE OR REPLACE FUNCTION to_base62_fixed(val BIGINT, width INT DEFAULT 5)
+RETURNS TEXT AS $$
+DECLARE
+    -- 62 chars of text
+    alphabet TEXT := '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz';
+    base62 TEXT := '';
+    r INT;
+BEGIN
+    IF val < 0 THEN
+        RAISE EXCEPTION 'Cannot encode negative numbers';
+    END IF;
+
+    WHILE val > 0 LOOP
+        r := val % 62;
+        base62 := substring(alphabet, r + 1, 1) || base62;
+        val := val / 62;
+    END LOOP;
+
+    WHILE char_length(base62) < width LOOP
+        base62 := '0' || base62;
+    END LOOP;
+
+    IF char_length(base62) > width THEN
+        RAISE EXCEPTION 'Value too large for % characters Base62', width;
+    END IF;
+
+    RETURN base62;
+END;
+$$ LANGUAGE plpgsql IMMUTABLE STRICT;
+
+
+-- Reverse from base62 string into an integer
+CREATE OR REPLACE FUNCTION from_base62_fixed(str TEXT)
+RETURNS BIGINT AS $$
+DECLARE
+    alphabet TEXT := '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz';
+    val BIGINT := 0;
+    c CHAR;
+    i INT;
+BEGIN
+    FOR i IN 1..char_length(str) LOOP
+        c := substring(str, i, 1);
+        val := val * 62 + position(c in alphabet) - 1;
+    END LOOP;
+    RETURN val;
+END;
+$$ LANGUAGE plpgsql IMMUTABLE STRICT;
+
+
+CREATE OR REPLACE FUNCTION obfuscate_id(id INTEGER)
+RETURNS TEXT AS $$
+DECLARE
+    -- hexadecimal value (denoted by "0x")
+    xor_key INTEGER := 0x5A3C1;  -- Any fixed number (you can change this key)
+    max_val INTEGER := 62^5;     -- Max value for base62-encoded 5 chars
+    encoded_val INTEGER;
+BEGIN
+    -- Apply XOR obfuscation, '#' is the bitwise XOR operation, aka bitwise OR, exlusive OR
+    -- compares bits of id and xor_key, returning a new integer where each bit is 1 if the bits differ, and 0 if they’re the same.
+    -- % modulo operator, remainder after integer division, this establishes an upper bound
+    encoded_val := (id # xor_key) % max_val;
+    -- RAISE NOTICE 'obfuscate_id id: %, encoded_val: %', id, encoded_val;
+    -- Return base62-encoded value with 5 chars
+    RETURN to_base62_fixed(encoded_val, 5);
+END;
+$$ LANGUAGE plpgsql IMMUTABLE STRICT;
+
+
+CREATE OR REPLACE FUNCTION deobfuscate_id(public_id text)
+RETURNS INTEGER AS $$
+DECLARE
+    xor_key INTEGER := 0x5A3C1;   -- Same fixed key as above, must say the same
+    max_val INTEGER := 62^5;
+    val INTEGER;
+BEGIN
+    -- Decode the base62 string into an integer value
+    val := from_base62_fixed(public_id);
+    -- Reverse the XOR operation
+    RETURN val # xor_key;
+END;
+$$ LANGUAGE plpgsql IMMUTABLE STRICT;
+
+
+-- Use generated always identity, primary key, use integer not bigint
+-- Use stored generated column for public_id, not null
+-- Use unique constraint on public_id (prefer to add using "using index" syntax)
+DROP TABLE IF EXISTS transactions;
+CREATE TABLE transactions (
+  id INTEGER GENERATED ALWAYS AS IDENTITY PRIMARY KEY,  -- 4-byte integer ID
+  public_id text GENERATED ALWAYS AS (obfuscate_id(id)) STORED UNIQUE NOT NULL, -- 5-character Base62 public ID, obfuscated
+  amount NUMERIC,
+  description TEXT
+);
+
+ALTER TABLE transactions
+    DROP CONSTRAINT IF EXISTS uniq_pub_id,
+    DROP CONSTRAINT IF EXISTS public_id_length;
+
+CREATE UNIQUE INDEX CONCURRENTLY IF NOT EXISTS idx_uniq_pub_id ON transactions (public_id);
+
+ALTER TABLE transactions
+    ADD CONSTRAINT uniq_pub_id UNIQUE USING INDEX idx_uniq_pub_id, -- depends on index above
+    ADD CONSTRAINT public_id_length CHECK (LENGTH(public_id) <= 5);
+
+INSERT INTO transactions (amount, description) VALUES
+  (100.00, 'First transaction'),
+  (50.00, 'Second transaction'),
+  (0.25, 'Third transaction');
+
+-- Make sure it's reversible
+SELECT id, public_id, deobfuscate_id(public_id) AS reversed_id, description
+FROM transactions;
+--  id | public_id | reversed_id |    description
+-- ----+-----------+-------------+--------------------
+--   1 | 01Y9I     |           1 | First transaction
+--   2 | 01Y9L     |           2 | Second transaction
+--   3 | 01Y9K     |           3 | Third transaction
+
+
+-- overhead
+DROP TABLE IF EXISTS transactions_base;
+CREATE TABLE transactions_base (
+  id INTEGER GENERATED ALWAYS AS IDENTITY PRIMARY KEY,  -- 4-byte integer ID
+  amount NUMERIC,
+  description TEXT
+);
+
+-- \timing
+-- INSERT 0 1000000
+-- Time: 2014.572 ms (00:02.015)
+-- Time: 2002.176 ms (00:02.002)
+-- Time: 2096.970 ms (00:02.097)
+INSERT INTO transactions_base (amount, description)
+SELECT
+    round((random() * 1000)::numeric, 2) AS amount,
+    'Transaction ' || gs.id AS description
+FROM
+    generate_series(1, 1000000) AS gs (id);
+
+-- \timing on
+-- "transactions" table with the public_id generation
+-- INSERT 0 1000000
+-- Time: 6936.973 ms (00:06.937)
+-- Time: 7120.707 ms (00:07.121)
+-- Time: 6804.530 ms (00:06.805)
+INSERT INTO transactions (amount, description)
+SELECT
+    round((random() * 1000)::numeric, 2) AS amount,
+    'Transaction ' || gs.id AS description
+FROM
+    generate_series(1, 1000000) AS gs (id);
+
+-- 6954.070 / 2037.906 ≈ 3.41× slower