SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'def36515ff35d7cd06ec20913e018202ef7448cae8fe0facde090d4763939ec4' 
  AND token = 'RbRhGPGjGHyLJANpV9VC2xmjr41bTNsdp3fmHisuepE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}