SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '768bc33302baa276d15f366e9bd75ed91595289f465ed1c23591d031c96da003' 
  AND token = 'rCV9GcebfeaxVEkmEyz4VjvAs2BSkKl5oL3EfmTcIQU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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