SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '7f9139929f7124889436e070f8011aa26017e32ce5640d391f1a0df613418193' 
  AND token = '5SxAt2n7LMebdPtwKvM2OQplfUOS2GdCJZELmg0zxtM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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