SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '688dc1db8fb96840195497d192da7317395f9be8e53778f0c80a765b0a541f0b' 
  AND token = '7piHXRhfmcDVAfwZv/B8FzS3k22hBRuxg3gGYHmXTwc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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