| Cover Page Cover Page | Dec. 09, 2019 |
| Cover Page [Abstract] | |
| Document Type | 8-K |
| Document Period End Date | Dec. 9, 2019 |
| Entity Registrant Name | MONGODB, INC. |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 001-38240 |
| Entity Tax Identification Number | 26-1463205 |
| Entity Address, Address Line One | 1633 Broadway |
| Entity Address, Address Line Two | 38th Floor |
| Entity Address, City or Town | New York |
| Entity Address, State or Province | NY |
| Entity Address, Postal Zip Code | 10019 |
| City Area Code | 646 |
| Local Phone Number | 727-4092 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Class A Common Stock, par value $0.001 per share |
| Trading Symbol | MDB |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0001441816 |
| Amendment Flag | false |
