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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a7f99ded178f7b21fb19ef9188135c796ff6ceb115b44aa8ff827e79f852e668' 
  AND token = 'g4YI8U1mHGdUbpdHcf8/XmLKOnGZBfaSKZqsgBH8z4k=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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