SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b994f11164d85b848576d10ae5993fe295d777053c5d12bb0bf8faada1f3c167' 
  AND token = 'MIHtMBFxJhHxeaBmcF8x47mAT+eSubT7lU0xfDyh6r0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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