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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '3c668843cc82644ebc19a9df88d21566681c18e4a5c64d7f4b8da11561cd2d67' 
  AND token = 'u0IiUYCO5oySSp938tq78OjfvWS+IuN0jpSzpmvDUTM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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