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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5f0c81341165bad3bdc0acfdba5e0edf229d2094bd4a07d6c9ad1cac9cc7fe20' 
  AND token = '6cl9oBdjK1octprwFQ+3+tifD83B+PqFqCp/B5sPB7Y=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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