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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c6c6d2339f042bb3242891bbeadfba02e3c22dfe04816270c16affddb0a8ebc1' 
  AND token = 'r5YNLLdxVoiLlSKf2yQghZ4QRboTWK9uzfcPVq/kjzU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}