SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c2017f426c3a343cd4e60b6416d69e8708672c0d62455bbb154d5073ae0c988c' 
  AND token = 'L3G/hzLXpnwuTPrvOfLijMqLU2emd9mVU3j7xUP3aXg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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