Senior Core Network Engineer in London

About Airalo

Airalo is the world’s first eSIM store that helps people connect in over 200+ countries and regions across the globe. We are building the next digital service that revolutionises the telecom industry. We are a travel‑tech company and an equal‑opportunity environment that values and executes diversity, inclusion, and equity. Our team is spread across 50+ countries and six continents. What glues us together is our commitment to changing the way you connect.

We hope that you care deeply about the quality of your work, the intrinsic worth of tasks, and the success of your team. You are self‑disciplined and do not require micromanagement in terms of your skillset and work ethic. You do your best to flourish as an individual every day while working hard to foster a collaborative team environment. You believe in the importance of being—and staying—authentic, honest, positive, and kind. You are a good interlocutor with clear and concise communication. You are able to manage multiple projects, have an analytical mind, pay keen attention to detail, and love to get your hands dirty. You are cognizant, tolerant, and welcoming of vulnerabilities and cultural differences.

About The Role

• Position: Full‑time / Employee
• Location: Remote‑first
• Benefits: Health Insurance, work‑from‑anywhere stipend, annual wellness & learning credits, annual all‑expenses‑paid company retreat in a gorgeous destination & other benefits.

Responsibilities

• Design and dimension the Packet Core (EPC/5GC) to ensure scalability for data growth.
• Manage roaming coverage with IPX/GRX providers, roaming sponsors, and direct bi‑lateral agreements.
• Define specific network profiles and configurations for HSS/UDM subscribers, including QoS, AMBR, and APN subscriptions.
• Architect the DNS hierarchy for the mobile core, focusing on S‑NAPTR records for MME/SGSN to discover PGW/SGW/UPF nodes.
• Plan and implement IP routing strategies, including ASN (Autonomous System Number) management and BGP peering for internet and roaming connectivity.
• Manage Access Point Name configurations for various service types, including IMS, Internet, and IoT.
• Perform deep‑dive troubleshooting of signaling procedures across 3G (Iu‑PS), 4G (S1‑MME, S11, S5/S8), and 5G NSA (EN‑DC).
• Apply in‑depth understanding of 3GPP standards for 3G, 4G EPC, and 5G NSA mobile data call‑flows.
• Analyze and optimize critical flows, specifically Attach/Registration (Authentication vectors, ULR/ULA, Create Session) and Bearer Management (Dedicated bearer creation for VoLTE/QCI 1 and default bearers).
• Utilize protocol analyzers such as Wireshark or Tektronix to decode ASN.1‑based messages and Diameter signaling (Gx, Gy, S6a, S5, S8, GTP‑C, GTP‑U).
• Act as the primary technical interface with core network vendors, system integrators, and partners.
• Lead technical evaluations and design reviews for core network expansions.
• Manage the ATP (Acceptance Testing) phase to ensure vendor deliveries meet operational standards prior to live deployment.

Requirements

• Experience with a Tier 1 Carrier, Mobile Operator, or Major Network Equipment Provider (NEP) background.
• Deep understanding of SGSN, GGSN, and HLR architecture.
• Extensive experience with PGW, HSS, SGW, and MME.
• Proficiency in 5G Non‑Standalone (NSA), 5G Standalone (SA), and PCC.
• Hands‑on experience with Diameter S6a (HSS‑MME), Gx (PCRF‑PGW), and Gy (OCS‑PGW).
• Strong knowledge of IP addressing, subnetting, OSPF/BGP routing, VRFs, and ASN management.
• Expert‑level DNS resolution (A, AAAA, SRV, NAPTR), DHCP, and IPX/GRX management.

Bonus Points

• Experience managing inbound/outbound roaming via Sponsor IMSI providers.
• Technical knowledge of GTP‑Proxy deployments for signaling and payload optimization.
• Practical experience working within an MVNO or MVNE environment.
• Familiarity with Regional and Local Breakout (LBO) strategies to reduce latency.
• Experience with Cloud Native Network Functions (CNF) and containerized core deployments.

If you are interested in this position, please apply via the link.

By applying, you acknowledge and agree that, in case of successful application, Airalo may request to run background checks as a condition for entering into an agreement with you. Rest assured that these checks will only occur upon your prior consent and at the end of the selection process, and will be strictly limited to what is allowed under the laws that are applicable to you. All data that you share or that we collect in connection with such checks will be processed in accordance with our Privacy Policy.

Airalo is an equal‑opportunity employer and values diversity, equity & inclusion. We do not discriminate on the basis of race, religion, national origin, gender, sexual orientation, age, marital status, veteran status, or disability status. We are committed to providing reasonable accommodations upon request for individuals with disabilities throughout our job interview process.

We may use artificial intelligence (AI) tools to support parts of the hiring process, such as reviewing applications, analyzing resumes, or assessing responses. These tools assist our recruitment team but do not replace human judgment. Final hiring decisions are ultimately made by humans.