SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21e794edde036761a2dce109125e119f9176fa09be6bccb337678968fa90080b' 
  AND token = 'd7ZPQAx/TqDQwfhVLKybftzrJtyHXpR7hCNTOF0RhPM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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