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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '7dffcb649ac5a36569bba09b66fdf37c19cb12ed1fb6923fef67aa1ff78da921' 
  AND token = '1Cmh+yV0NrJeerlHeLSaiPYq6QqSqdTezqhUZSHhjAQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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