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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'c9f71fb03a4163246d05ab0a90245ee6da52330003d11c9223a52145303eacf1' 
  AND token = 'WDQnzVeUQ0AFpm7+QkytgHFQiqWudKHC0E81grjW9VU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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