SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '76acaa18ea455b74cf7e19834720d8782f7138961090de2a3cf917cc790adc9c' 
  AND token = 'mtE+uBfA4lz3IQpngQVYyBYKqJpHjIwtFDNRnIm5veA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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