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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fff7c387ed9dc24dfd289ad95666c7ee1726140da2c3bfecfdf3ec72d63d3db3' 
  AND token = '8/nMvIVabvoyDMtYqiQKxLJl+bpnZd7+y8ebn53WlAQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00047

JSON explain

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