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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c5dd1420ca1d7360def16367ec74535ce14944a4745431f6053c92ae5cdb3836' 
  AND token = 'stTUAqBD4RnVpfuEdfWzrqMZDhoOg3XcmylCNtsT+SM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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