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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6751e122a3022639b7cc36b132e5a4bb74adf0cb3ba2189d4b616a9a66d073df' 
  AND token = 'WYTtVj01ImRxRNgh3fhdm81kLz3w55IycKfXeFnhURs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00016

JSON explain

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