SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f4b3162f7da014c8cc22ed979e20f4a8bb59e53eb57ee8d864a0b38f7ff5a526' 
  AND token = 'QEqDvIfFhLKPSvu5rWQUQokjXuZoyT3VNNtqhXpDprg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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