SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b8a0d13b83f1231d81c8c9cd3beee925fe44a68ced58a073a4b0f558f11d44ee' 
  AND token = '6PqZaG07slw8HMNbRYIsTl0RkRBuhSetBMA+3KXlSks=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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