SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '76eb7bdf93d9c471635824aebc6b578afc3d46d3fa1a559adeff05a9e4117233' 
  AND token = 'tp6mT+fWIvjKoYwokXSgy/Wx1hhF5DPKjZIahka92Aw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00047

JSON explain

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