SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '42b68d003ef0986dde1d64a0aa1d2f238aa0345b6ef22d76e551340b0e5b8590' 
  AND token = 'upz97v3/RuAi04uXVuxKBPJIsp2XJrrpj+gJYt52g+M=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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