Learn Hardcore Indonesian: Meja di kafe itu sudah dipesan untuk rapat. - The table at that cafe has already been reserved for a meeting.

It marks completion/aspect, roughly “already/has been.” Indonesian doesn’t mark tense on verbs, so sudah tells you the reserving is complete. Variants:

telah: more formal/literary.
udah: colloquial. Negative counterpart: belum (“not yet”).

Why is the passive dipesan used instead of the active?

Indonesian often uses the passive to foreground the thing affected (the table) and omit the agent. Active would be:

Kami sudah memesan meja di kafe itu untuk rapat. (We have reserved a table...) Passive is natural when the agent is unknown/irrelevant or you want to focus on the table’s status.

How do I include who made the reservation?

Three common ways:

Passive with oleh: Meja di kafe itu sudah dipesan oleh kami untuk rapat.
“Passive type 2” (agent pronoun before the verb): Meja di kafe itu sudah kami pesan untuk rapat.
Active: Kami sudah memesan meja di kafe itu untuk rapat. Note: kami excludes the listener; kita includes the listener.

Does itu modify “café” or “table” here?

It modifies the nearest noun, so kafe itu = “that cafe.” The phrase means “the table(s) at that cafe.” To make “that table at the cafe,” attach itu to meja: Meja itu di kafe (itu) sudah dipesan… If you want both to be “that,” say Meja itu di kafe itu…

Is meja here singular or plural?

Number is unspecified unless marked. It can mean “table” or “tables.” To specify:

One table: sebuah meja / satu meja
Several tables: beberapa meja
Two tables: dua meja
Plural emphasis: meja-meja

How do I say “not yet reserved” vs. “not reserved”?

Not yet: belum dipesan (implies it may be reserved later).
Not: tidak dipesan (a flat negation, no “yet” nuance). Examples:
Meja… belum dipesan.
Meja… tidak dipesan untuk rapat.

Why is di separate in di kafe but attached in dipesan?

Two different “di”:

di (separate word) is a preposition “at/in.”
di- (attached) is the passive prefix on verbs. So you write di kafe but dipesan.

Should it be di kafe or ke kafe?

Use di for location (“at/in”). Ke means “to/toward” (movement). Here we’re talking about location, so di kafe is correct.

What does untuk do in this sentence?

It introduces purpose: “for (the purpose of).” Alternatives:

buat: informal, very common in speech (… buat rapat).
guna: formal.
bagi: “for (the benefit of),” not usually used for purpose with events.

Is rapat the only word for “meeting”? What about pertemuan or “meeting” as a loanword?

rapat: standard for work/organizational meetings; quite formal/common.
pertemuan: a meeting in the sense of a gathering/encounter; broader.
“meeting”/“miting”: loanword used in some corporate speech; in careful Indonesian, prefer rapat.

Could dipesan mean “ordered” (like food), not “reserved”?

Yes, pesan means “to order” or “to book/reserve,” and context decides. With meja (table) plus di kafe, it clearly means “reserved a table.” With food: Saya memesan nasi (I ordered rice).

Can I change the word order?

Yes. Some natural variants:

Di kafe itu, meja sudah dipesan untuk rapat. (topicalizes the location)
Meja di kafe itu sudah dipesan untuk rapat. (original; keeps the location tied to “meja”)
Meja sudah dipesan di kafe itu untuk rapat. (still fine; “at that cafe” can modify the reserving event) All are grammatical; choose based on what you want to foreground.

How do I ask this as a yes–no question?

Neutral/formal: Apakah meja di kafe itu sudah dipesan untuk rapat?
Colloquial: Meja di kafe itu sudah dipesan untuk rapat? (rising intonation)
Soft check: Meja di kafe itu sudah dipesan untuk rapat, ya?

How do I make “for the meeting” specific (not just any meeting)?

Add a determiner:

untuk rapat itu (that meeting)
untuk rapat tersebut (that aforementioned meeting; more formal/back-referential)

Is untuk sebuah rapat okay?

Yes, but Indonesian usually doesn’t need an article here; untuk rapat is default. Use sebuah if you want to stress “a single, specific instance,” often with an adjective: untuk sebuah rapat penting (for an important meeting).

Are there other common ways to say “reserved” for restaurants?

Yes:

sudah direservasi / melakukan reservasi (from “reservasi”; common and acceptable)
Informal: sudah reservasi meja
Very informal/nonstandard in formal writing but common in speech: dibooking / membooking Standard Indonesian prefers (di)pesan or (di)reservasi in careful contexts.