SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '668b264f68638e126255a740571fb013388928c0a1c389367ebb256dcf5d6659' 
  AND token = '/WEp81ASPwpzCIKon8h+pCVwroCQ4qcNPtUnyVGq5kY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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