SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '42186f65364c6cfd916d4794611b7d2570991ae475de9467124f77b1e206df5a' 
  AND token = 'MDZGGDmGwFhPzB2BvQFxVkMj4/gQoCX7p6IMZnAHBFI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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