SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c5c4a8588d9a825e2652eaa90138f38e9084e70c1b0616217fde92eb43c40717' 
  AND token = '+51D3z7HOSr2zIUsz/s2K3MiYWDsmNqVS/JvfawgzCM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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