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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '75bc28d9afd15c8385afe722bd8de6a3a91c5eadba860f8d3f2b7be500106ffa' 
  AND token = 'ZJPmEfNM6p603syQrtlOuVujWMntC4T9knlaDCZUQCA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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