SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a4e6ffdb9400c8979125816f72af112fe7bcc7751aad4352cfb8cde5c652d05d' 
  AND token = 'Z5gMb/9j+IUciFLXgWw5YloPNyRNEWyBVpjU6W5a2aI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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