SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '75b86c527a5a79a98f522a3cd1ac31162c402ac8ca5b4e36c8daa03bf36821bb' 
  AND token = 'MnW6xNRNaKPLQ9KnuRzfvJOeV+wmpuwkOvMBS+HhkSU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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