SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a0550773baaaa2f558fd9dffe0caa5ba829fe7b4538f641812205e8a66d7a9ba' 
  AND token = '4xEFwtOG2hfRaWAqQOcgdeW0zLatij8spFQEvEisijs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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