SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51df9f391bfe5bfeef49b47f0dcfc62a691731ef0f16ca2801a2a942fa586869' 
  AND token = 'L+ZemD8qDmweyYElVdNgcKP/ynKEmo/I3UQUjnBUDl4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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