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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '375b71e6f695895df44303f53d979a62176da6156e8fe673584afea90fc35178' 
  AND token = 'QywBmN28oRZb6dN4Or2LrF9WqmpLcaf+De9T3UHouGA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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