SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b8721c2ce912f1f6c2b6c17855ebc398af9085982476dd4e5aee1982bf5023b6' 
  AND token = 'vrKPdQAQvTRznQ+cYtHzam1/Zbh3s1Izfclh+E4W7lw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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