SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e426d2c72be5b5d3ee6ba5eb014a4f4f300aecd2948d0cbfff587bbd0fd9bd6b' 
  AND token = 'mcSFnapSwBSkgWCQOqNzuZuFK4IDof0VNl/qLw9Wbww=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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