SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ff1f884dc5fd099d07a8336f3030044cba703ee67697078b0855f62bc3b5c519' 
  AND token = 'zlCbOX4zqPHLYsEV5cBWrBLWDio8mu0ciOoylzVycFE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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