Practical highlights in my opinion:

• It's important to know about data padding in PG.
• Be conscious when modelling data tables about columns ordering, but don't be pure-school and do it in a best-effort basis.
• Gains up to 25% in wasted storage are impressive but always keep in mind the scope of the system. For me, gains are not worth it in the short-term. Whenever a system grows, it is possible to migrate data to more storage-efficient tables but mind the operative burder.

Here follows my own commands on trying the article points. I added - pg_column_size(row()) on each projection to have clear absolute sizes.

-- How does row function work?

SELECT pg_column_size(row()) AS empty,
       pg_column_size(row(0::SMALLINT)) AS byte2,
       pg_column_size(row(0::BIGINT)) AS byte8,
       pg_column_size(row(0::SMALLINT, 0::BIGINT)) AS byte16,
       pg_column_size(row(''::TEXT)) AS text0,
       pg_column_size(row('hola'::TEXT)) AS text4,
       0 AS term
;

-- My own take on that

SELECT pg_column_size(row()) AS empty,
       pg_column_size(row(uuid_generate_v4())) AS uuid_type,
       pg_column_size(row('hola mundo'::TEXT)) AS text_type,
       pg_column_size(row(uuid_generate_v4(), 'hola mundo'::TEXT)) AS uuid_text_type,
       pg_column_size(row('hola mundo'::TEXT, uuid_generate_v4())) AS text_uuid_type,
       0 AS term
;

CREATE TABLE user_order (
  is_shipped    BOOLEAN NOT NULL DEFAULT false,
  user_id       BIGINT NOT NULL,
  order_total   NUMERIC NOT NULL,
  order_dt      TIMESTAMPTZ NOT NULL,
  order_type    SMALLINT NOT NULL,
  ship_dt       TIMESTAMPTZ,
  item_ct       INT NOT NULL,
  ship_cost     NUMERIC,
  receive_dt    TIMESTAMPTZ,
  tracking_cd   TEXT,
  id            BIGSERIAL PRIMARY KEY NOT NULL
);

SELECT a.attname, t.typname, t.typalign, t.typlen
  FROM pg_class c
  JOIN pg_attribute a ON (a.attrelid = c.oid)
  JOIN pg_type t ON (t.oid = a.atttypid)
 WHERE c.relname = 'user_order'
   AND a.attnum >= 0
 ORDER BY a.attnum;

-- What is it about pg_class, pg_attribute and pg_type tables? For future investigation.

-- SELECT sum(t.typlen)
-- SELECT t.typlen
SELECT a.attname, t.typname, t.typalign, t.typlen
  FROM pg_class c
  JOIN pg_attribute a ON (a.attrelid = c.oid)
  JOIN pg_type t ON (t.oid = a.atttypid)
 WHERE c.relname = 'user_order'
   AND a.attnum >= 0
 ORDER BY a.attnum
;

-- Whoa! I need to master mocking data directly into db.

INSERT INTO user_order (
    is_shipped, user_id, order_total, order_dt, order_type,
    ship_dt, item_ct, ship_cost, receive_dt, tracking_cd
)
SELECT true, 1000, 500.00, now() - INTERVAL '7 days',
       3, now() - INTERVAL '5 days', 10, 4.99,
       now() - INTERVAL '3 days', 'X5901324123479RROIENSTBKCV4'
  FROM generate_series(1, 1000000);

-- New item to learn, pg_relation_size. 

SELECT pg_relation_size('user_order') AS size_bytes,
       pg_size_pretty(pg_relation_size('user_order')) AS size_pretty;

SELECT * FROM user_order LIMIT 1;

SELECT pg_column_size(row(0::NUMERIC)) - pg_column_size(row()) AS zero_num,
       pg_column_size(row(1::NUMERIC)) - pg_column_size(row()) AS one_num,
       pg_column_size(row(9.9::NUMERIC)) - pg_column_size(row()) AS nine_point_nine_num,
       pg_column_size(row(1::INT2)) - pg_column_size(row()) AS int2,
       pg_column_size(row(1::INT4)) - pg_column_size(row()) AS int4,
       pg_column_size(row(1::INT2, 1::NUMERIC)) - pg_column_size(row()) AS int2_one_num,
       pg_column_size(row(1::INT4, 1::NUMERIC)) - pg_column_size(row()) AS int4_one_num,
       pg_column_size(row(1::NUMERIC, 1::INT4)) - pg_column_size(row()) AS one_num_int4,
       0 AS term
;

SELECT pg_column_size(row(''::TEXT)) - pg_column_size(row()) AS empty_text,
       pg_column_size(row('a'::TEXT)) - pg_column_size(row()) AS len1_text,
       pg_column_size(row('abcd'::TEXT)) - pg_column_size(row()) AS len4_text,
       pg_column_size(row('abcde'::TEXT)) - pg_column_size(row()) AS len5_text,
       pg_column_size(row('abcdefgh'::TEXT)) - pg_column_size(row()) AS len8_text,
       pg_column_size(row('abcdefghi'::TEXT)) - pg_column_size(row()) AS len9_text,
       0 AS term
;

SELECT pg_column_size(row(''::TEXT, 1::INT4)) - pg_column_size(row()) AS empty_text_int4,
       pg_column_size(row('a'::TEXT, 1::INT4)) - pg_column_size(row()) AS len1_text_int4,
       pg_column_size(row('abcd'::TEXT, 1::INT4)) - pg_column_size(row()) AS len4_text_int4,
       pg_column_size(row('abcde'::TEXT, 1::INT4)) - pg_column_size(row()) AS len5_text_int4,
       pg_column_size(row('abcdefgh'::TEXT, 1::INT4)) - pg_column_size(row()) AS len8_text_int4,
       pg_column_size(row('abcdefghi'::TEXT, 1::INT4)) - pg_column_size(row()) AS len9_text_int4,
       0 AS term
;

SELECT pg_column_size(row(1::INT4, ''::TEXT)) - pg_column_size(row()) AS int4_empty_text,
       pg_column_size(row(1::INT4, 'a'::TEXT)) - pg_column_size(row()) AS int4_len1_text,
       pg_column_size(row(1::INT4, 'abcd'::TEXT)) - pg_column_size(row()) AS int4_len4_text,
       pg_column_size(row(1::INT4, 'abcde'::TEXT)) - pg_column_size(row()) AS int4_len5_text,
       pg_column_size(row(1::INT4, 'abcdefgh'::TEXT)) - pg_column_size(row()) AS int4_len8_text,
       pg_column_size(row(1::INT4, 'abcdefghi'::TEXT)) - pg_column_size(row()) AS int4_len9_text,
       0 AS term
;

SELECT pg_column_size(row()) - pg_column_size(row()) AS empty_row,
       pg_column_size(row(''::TEXT)) - pg_column_size(row()) AS no_text,
       pg_column_size(row('a'::TEXT)) - pg_column_size(row()) AS min_text,
       pg_column_size(row(1::INT4, 'a'::TEXT)) - pg_column_size(row()) AS two_col,
       pg_column_size(row('a'::TEXT, 1::INT4)) - pg_column_size(row()) AS round4;

SELECT pg_column_size(row()) - pg_column_size(row()) AS empty_row,
       pg_column_size(row(1::SMALLINT)) - pg_column_size(row()) AS int2,
       pg_column_size(row(1::INT)) - pg_column_size(row()) AS int4,
       pg_column_size(row(1::BIGINT)) - pg_column_size(row()) AS int8,
       pg_column_size(row(1::SMALLINT, 1::BIGINT)) - pg_column_size(row()) AS padded,
       pg_column_size(row(1::INT, 1::INT, 1::BIGINT)) - pg_column_size(row()) AS not_padded;

SELECT a.attname, t.typname, t.typalign, t.typlen
  FROM pg_class c
  JOIN pg_attribute a ON (a.attrelid = c.oid)
  JOIN pg_type t ON (t.oid = a.atttypid)
 WHERE c.relname = 'user_order'
   AND a.attnum >= 0
 ORDER BY t.typlen DESC;

DROP TABLE user_order;

CREATE TABLE user_order (
  id            BIGSERIAL PRIMARY KEY NOT NULL,
  user_id       BIGINT NOT NULL,
  order_dt      TIMESTAMPTZ NOT NULL,
  ship_dt       TIMESTAMPTZ,
  receive_dt    TIMESTAMPTZ,
  item_ct       INT NOT NULL,
  order_type    SMALLINT NOT NULL,
  is_shipped    BOOLEAN NOT NULL DEFAULT false,
  order_total   NUMERIC NOT NULL,
  ship_cost     NUMERIC,
  tracking_cd   TEXT
);

-- And, what about other varying size types as JSONB?

SELECT pg_column_size(row('{}'::JSONB)) - pg_column_size(row()) AS empty_jsonb,
       pg_column_size(row('{}'::JSONB, 0::INT4)) - pg_column_size(row()) AS empty_jsonb_int4,
       pg_column_size(row(0::INT4, '{}'::JSONB)) - pg_column_size(row()) AS int4_empty_jsonb,
       pg_column_size(row('{"a": 1}'::JSONB)) - pg_column_size(row()) AS basic_jsonb,
       pg_column_size(row('{"a": 1}'::JSONB, 0::INT4)) - pg_column_size(row()) AS basic_jsonb_int4,
       pg_column_size(row(0::INT4, '{"a": 1}'::JSONB)) - pg_column_size(row()) AS int4_basic_jsonb,
       0 AS term;

The NSA must be psyched about this.

How is information, for example, a conversation accounted for in this model? As we go forward and find more efficient ways to store and convey information in fewer 1s and 0s, must we constantly reevaluate this relationship? Passive vs Active storage of information seems to be key here as well.

this is the storage question everyone always goes to 1st when we use the word "data" in libraries. Is there possibly another question we should ask first?

Is access private/public?

This point seems to be in direct contradiction to the claim above that "Indexes (primary and secondary) are always stored in DRAM for fast access and are never stored on Solid State Drives (SSDs) to ensure low wear."

Does this really mean to suggest that Aerospike bypasses the linux block device layer? Is there a kernel driver? Does this mean I can't use any filesystem I want and know how to administrate? Is the claim that the "linux file system" (which I take to mean, I guess, the virtual file system layer) "built for rotation drives" even accurate? We've had ram disks for a long, long time. And before that we've had log structured filesystems, too, and even devices that aren't random access like tape drives. Seems like dubious claims all around.