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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '03eed51bd4854aa187ce020d5b7f5182616ec575fbd315a9be4aa76682540ac2' 
  AND token = 'xxx6AUqr2xI5YlG+PXavamEjs63zGTn30GdwBfs9hh4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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