SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c520484ff5b239f200ac56a86f0df2ede920024f8de91920e86bd23be1baa476' 
  AND token = 'oC3HWDpwnh7CWfA5XFtc8oSipnjTFGjqflFs++WlP2s=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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