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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '8a0cb9c0b199f2bf547e8fafd65809b9135f8fa6436ff62047245d976b6abacd' 
  AND token = 'diElRKH+S1j3Kr2uO7fEe5ZcSCndpZvDKNx2SiaXOkU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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