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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '355788f11888b29ac1836ad0a5dcbe21fe0b344b8034d7f6626707a9de6a073e' 
  AND token = 'QqisfMd/3sbIv7Hgu+KbmHOM6K/MMmxeEkt1k/LJE+s=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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