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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5ad8be81c75eca6af617d0f49be1b5371737fa7c5c5035f0a6a7a7ca9e239cda' 
  AND token = 'E5dMR6NQtnCjC2M7FgF3rNpY+GKI0hvRpTeoUSBAWCE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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