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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'cfbb66d04d78ee883e6dd189955c9965d2adeb88d4584dc4b73016bad50e61a4' 
  AND token = 'ZdVgHuRemuZ2g7ZaVbxpjX+pAFtRRxwE8VmCc49HeU0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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