SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c6ce462a4df7cbbf60e8b34aa9aaa1f9efa5b81b7ac15889f848ecbbda356d73' 
  AND token = 'B7rGIiMmzYws+iu7p1z+gFk1IPsY/sOVkiCKGmB3FQc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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