SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6b6a74717315c67dcb906fb3a703d4b88303d30cb71ad0a1c902ca5a27aa0f81' 
  AND token = '18eGUuEyWzruLwmgf3jbsfcb3vq7rc2xUWW2IgvtwQk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}