SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '2321b1ebb6368e0764ea0020a518664bfc94695ffefee1bf983656191d67f91b' 
  AND token = 'h2ZQiABWKEcMBmnZCvPAKkQPBm3nGFaRBLAM5+Ehu6Y=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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