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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'eab6f36b44afa04a112c84458d9507251fe209db184542e9d65065f69beb61b2' 
  AND token = 'QtYcTs5m5ZbRPhEz6BkhEW4+G+z7P0LlEaIeC//+8Z4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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