SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6ec3967db8763afd7af79912291f986c3b76c8db7918b46fd9ca024d31a96798' 
  AND token = 'G30zXRWKZEAhV7lxefS4xaBI8warKcEIWIJ/IPnAyn8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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