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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a21ec9935af8721e8bb382e1e1fd6f2df54b65a98c30725c083235375f37e0e9' 
  AND token = 'PUl+OdfE3vQVbV8XSiL+Vukh/DPrSIOT7T+vvtwqZDI=' 
  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"
    }
  }
}