SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '283c606256a1e466ea72904c6817927e2a3a01a9bae0653e81c4464cac873444' 
  AND token = 'b9ikiQEQoJMf9451xqq0Y5WYGQDXcRFdwUkPzBpsGeY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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