SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b6d623f4861f15ea6bce0d09bcda1c97bc88e93e34662e720aa574fbadddb799' 
  AND token = 'ewYyQiPklgxmplstkL8D1Rfy7D6JSXw87mzfRPHaqVY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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