SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f8713527bbe83fdf29012192bf556315885a336ea82fa101e40699763cfb9e92' 
  AND token = '8QhNe/hb5XzYzB3vq+uUfEWGxjcgd5kYtwbyBvFMRs0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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