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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '31a692d87b8b4b50df3e64c2132ac3b676a511eb4f0eabaa6c3487615e85cf36' 
  AND token = 'MLJu5npuClv8Yl5BD25Bn4LBklaCJQUixtLqPi+Al8c=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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