SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f3bfd4248fca698786377164024043e77ffdefea275765676d083250636218af' 
  AND token = 'qNnxzoeKILfjmJHYtjGyO9jndWleEr+jbRv5ecR5qZY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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