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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b8e1eaad71927fed3ef2a21c996d2f55586c8fc9c729e056adea61517252f10d' 
  AND token = 'PCrMTb9hUfJVDhhrrDia2/91zXtala5DNBLto2XHnng=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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