SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'dd8ceab8c6b88a460655817e7c895f1d135230ef0d4ad97095be4642fb694ce5' 
  AND token = 'ET/KH81NldOhA+ysQepdue4NWKocVwq+wvnCQVRzYxE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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