SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8c43e7249d901b84013597523e8e941169eaac9094858d947c919928a940da1d' 
  AND token = 'DmE4jgbSKOvA1fRNOqeahefZK8aUn9y3IISscrLjZhU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

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