SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a238ea76d37ec3842cef546281b7d7187fe63cc7e5a13e5e651af57987bb0545' 
  AND token = 'OXwDUlP9VxRPV5bFXft8hk+bbGrcmk1t5S5M8khvAQM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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