SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51df32e556566dfc3814f41870bb97db3c693f194081610d453efc2b0ae8fd74' 
  AND token = 'rFQYyqoFRJRM13CXTAQgAE840cVKTFe+rCbg8B/JzFU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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