SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e19e52c908a2e0e91f78441f8f52627bb6faef6be5e3512de365e5235aba48a4' 
  AND token = '6VMawzYLKlDFiNpXmw4wATycXFVg+6upFc3MMWVEwIk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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