SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '7a787992298d748dd5e4024633d49dc884c6aa9d5efdd605238c92d25292db52' 
  AND token = 'n0e9y0eVCT7yKq3QFaFqCcVmAGfqxISrXLiNKJE100U=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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