SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd4c784df225cc59d5380afa24e92122e76905f6ddf06a94710e6a8e84afa6970' 
  AND token = 'RMn6uzgTxvcYfDKUZShu8lxjzrIl5IW9XYz+6hqZ+/c=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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