SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'bf615aadd248afab5682ce93b2fe35bd489666ac576644bbc02531347c271554' 
  AND token = 'Ac8XOuhIZgOsP0ayrL8QTBeQD9kHj5kBvi35IO0UW54=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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