How can I paginate Firestore results between a lower and upper bound using query cursors without fetching previous pages?

Firestore cursor pagination between numeric bounds works when the bounded field is also the field used in orderBy(). If the population field drives both the range filter and the ordering, you can derive a start cursor for page N by capturing the last document snapshot from the preceding page and applying startAfter() on a reused base query.

Likely approach (forward pagination)

1. Construct a base query that constrains the field to your lower‑upper bound and orders by that field:

db.collection('cities')
  .where('population', '>=', 1000000)
  .where('population', '<=', 5000000)
  .orderBy('population')
  .limit(pageSize)

2. Execute the query and keep the first and last document snapshots of the returned page.
3. To move forward one page, reuse the same base query and append .startAfter(lastDoc):

.startAfter(lastDoc).limit(pageSize)

4. To move backward, keep the first document of the current page and use .endBefore(firstDoc).

Confirmed constraints

• The range field must also be the orderBy field; otherwise cursors do not advance as expected.
• Cursors are snapshot‑based: each query reflects the data state at execution time. Adding or removing documents between queries can cause duplicates or gaps on subsequent pages.
• Reusing an end cursor across multiple pages is safe only while the dataset remains static; otherwise recompute the cursor from the current page's first document.

To verify the approach works for your data, confirm that the field used in where() bounds is identical to the field used in orderBy(). If they differ, cursor‑based pagination may produce unexpected results.