SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8da7a1c50aea3cd6244bbd091e535312dc90dce349c640dca720afefe89d08ec' 
  AND token = '+1wx8UcDr3ZfqlhtFZtP2ekqUW6SPYlikqMj/eB86kU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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