SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '19e9abc846b2990c904c23c5252d03a3dbf87a302071557f58d05d0c137513ea' 
  AND token = '5/4//gWwxqJi6ohZwYCSK3FXcKmSOfWCxXpPZhwDR80=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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