SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6ccb72b952ced7a612077b49e5a1c97d50888e6851812a21faaf355991966966' 
  AND token = '8BCvfzCN85hMqEMBhxVMgg+6J0UJg6fDOmmd/ZhKROs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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