SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fc5b805b86f78fa49ea61c97191ae2b6b39dfa9078b670f98fbe735a911f76d9' 
  AND token = 'UhLDZThegR2brNThgo80+IroJ7luUdAsudhuXQOuUt4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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