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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '975306a33059298f6271f114ea8d4e7daba7ac01cd47f008a0e24e548520f5f8' 
  AND token = 'fRC5ev4GvirxnTNL9QeF0xTWZoqHW75qS3h71GoYMm8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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