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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '0dd39c68294753758542aabf9c870da32eccc240f634510e063c4539cfdf4ea2' 
  AND token = 'Je6Daxeu47Rmt2LRNLwZEbGLd7Abs8F5/fZkvqO0uTw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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