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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '720be8103e106cdde544f70b33e76dc17ce6c2e2fa5d9365d3a21000303c7115' 
  AND token = '3ydxhUGvqvxcAmrr6uMXlcZ9i7lBjfdUMmKpAaDlFDw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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