SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '7876752c712272d1234f9cb59d754eb189cf84bf36577f511454901583dc69b1' 
  AND token = 'SLD+JiVwsutnLfJvaAi/imUzmL42/hFgJ86GaTCLXu8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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