SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3b256a0886de21d886f5bc8fb9014e6e9fccdf338a436ce0cf6811a5a1f62138' 
  AND token = 'zxm8TPgjmXcwMQkBeKZuiOk30kNTPijJ4rAGIrfNh7o=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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