SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '50ddea4623f3918c97099bd33633e8cbb408cebc2826dcfe60d34cb9f03d5f9c' 
  AND token = '4jJKTZHKlftC4YW0KqBWH5VC2OwJBs5CmfD6pez1zAg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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