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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '81e0c670093613e73899c33cc6f6ce98f96da0212db8fb7a3a7d768dae35634d' 
  AND token = 'hQiJLcHQW1+M8lTueqy1AHT7rCKThyDZNi9j6FVlk3E=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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