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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '640cc19861794bd3fdc6a4ddf70b938f979ec85e7b9ba61a1a7e1ab6fed7af1a' 
  AND token = 'Xt3ZPcIenHcpHovcdlwVeiu1ZqLErO1O83k+2ibhMlI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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