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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'd3690fe3a4390adebe016080a3ec37e9b51183d5d73bd9033269320da37a8342' 
  AND token = 'X6aS0BAOTiE5ON1XFyOp8YxwwOqsB9dIvylEUNt1El4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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