SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '831cc710de9d2ffec87d22fee2e3e67891b53c927c2aef6836cba74e169052e5' 
  AND token = '1vJ7yaP6Az8o9MgdCdm2PxZWekD1xD7DJ+bGfgLh+jM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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