SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fe678ade8c7b575fe8f153c29d7c92834745eb602247f1b2a29cf4d0b9f1fa17' 
  AND token = 'FM7+tR8JJDe3dQa3pZU0sY7rI9CxxQszRgzrh5VCPUk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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