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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'c3ef1c1f7a684c8ed453ea58e07f7613657883e60b67faac4bfd0b12043e82cf' 
  AND token = 'rb+b96E0y2agzrhbd9VFaJQ5trJY1xuKXLD7ZxiTpPM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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