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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c4b3340aee04d9b48edeabffd3e69e36f273b9537f7e4ccd75e1004e1824ee74' 
  AND token = '0N9qaKU8QBDi1cJZ9XKVYuyp1kVhmV3OzhfP+q6tEQQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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