SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c9d55cc2d1866b984313b45cd40d1606ecfe211781a764a7623896a0b33b9002' 
  AND token = '3k7jaxdefAiBDO4M6ALwkHWsPREUChlwXthFj+hK37s=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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