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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '5b0cb15e49b9efaec442f171c6f9b7c15bfa9890592f467fb05df970a16be473' 
  AND token = 'nBzks0edzUL9jXyZJRC0cf9s1bUuq7syhfVbIBdWcVo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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