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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'e6698c36e735600ccc10312d0542e4ac9dd8cb12a657e5d74bfdf404d76a1667' 
  AND token = 'uPAM5+Hyx3YBXjWCaNGXfbEkbEzjlIiiqoG8hTEpDzk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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