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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6b65c406d4e4f7229c0f2dc974e0d6108b5ebdf8ad75ad52661ccabd5e7ecb23' 
  AND token = '4R2Y0ViOudn5Dr/rVJ6Fn8yFEEDkkcEqj0n9+UtgViQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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