SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6a475c3b52efbb12ac0893351667348e5b922c514a1dd76d851f471182dde36a' 
  AND token = 'x8sU9pLZ2f+CQFAWSNUfgDUawH9AY7Ifj2BlD2CVo/s=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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