SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd3786434c0ec4d335ebb60813a9001ae3abc5509dda552703baa72f2dd35e0be' 
  AND token = 'llEhewZTcu9o+96nrwdPjmiyoJWNM/GmkjIxxhHp34g=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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