SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '9403186c9bdbea71befb5a1843a13ba1879f3f58a2d99bbd32e08a796e7a3e6c' 
  AND token = '+BjYHgWRlLM6v9aOu9OV6GnWYLBxJwjlQ2io5Cvb99w=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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