SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '915b3e830095eba526fdf5886d7eba480e08db126c0496a569829ab3494a801b' 
  AND token = 'Ka1YX+/hrIIoRX6548W+qE0a7hq9BrinrlKKTTJMgWQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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