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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'db550ff9c01cbed509141cc60243ece08fb4da72b0b2b477483948cd5e083c49' 
  AND token = 'BtMQGt5y0JnBE5HQ2uRk35it+QqotazMgzCSAs82zsw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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