SELECT 
  1 
FROM 
  cscart_june_setuplock_keys 
WHERE 
  key_id = '51c8f3d90d572094376f01758a35976af57b6cf23f0d05e84bd07f455287ad77' 
  AND token = 'VKOS8dhRPg0xu2923rGFCkSGO9h7jHN2meUi6zOLSqY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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