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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'a6d9a73907a35b95fefd0a1eb7dfeec7898a7129274d9f929609515c0eeac0d0' 
  AND token = 'zHN545zb65NNWTr3/ZfpcS9VyIM75XyOwSI2KRlfPCw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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