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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6d8e88c638217737efcf1b396ef5e76617824c3a739d53f12f1a8a147bb78e66' 
  AND token = 'mDmTf+MMin8bPf6YhAVNFihVNYS+Qdog7AG1H7/qp7k=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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