SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '68c8be5962d55e73186dce6fbac4b39c3da643de71a6208d8758fc1d0def640c' 
  AND token = 'ya7dz0L8RCiMwFhJ9hRKoO3W5Avj8nFJ8AMY0gvZCL8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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