SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '021e23fe9af1cf0233a4808d4095d6448c3b830a470223c87943b65759eca711' 
  AND token = '+iRpkBaROEQLJpLPpNf/fulw1cUIzIMkDpKrKtnTkyQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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