SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '1cfd27c1f978644a5d24d59c868f918d4e07f0135d235de8366fee819438f3c2' 
  AND token = 'dNremlK55WWnjdomTkzCvSn1w9TDUBwyBEciNH+1nYA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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