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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51f212c5a43fc7fc5f5b84db78095322980bca65ebce4321f073e3e08a8224ad' 
  AND token = 'bWe9TF5HvfYCW3qXeaI3CT/jRXgVmMd+kFkDWiIem7Q=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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