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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '321a9954060d510e9687fe40e7763ed24719fe34eadf715eae311eaa7cde8197' 
  AND token = 'YsZByAT+4stC1SeJM+18a9WTNxKeN05Vn1hHkbeojY4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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