SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21f12b7ead9943cb71893f615f51d2ca0477ee345f8e3502533e1403a230d282' 
  AND token = 'AqRezpKxealkEp3EriDjtFQZ8QbOy5MSdUphHt4juYQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00016

JSON explain

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