SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c12d5ac64cd00cb1c43400525326522359d81977424bb829d6be4789ee6cf7d9' 
  AND token = 'GKHfgYYL0kF65xkZsFDoEJIDNj+Q6qumqvDSiivluoA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}