SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6834930f6865b1033588d9bab0d652d615a06cddcaec2312ff1e721627bcce62' 
  AND token = 'fHs0HGZVmaTgk4/OPwhjnhJVvOXFJb/W+GUiEtO53Xg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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