SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a8c249218d71b8972d0a3682e7ab673f3e419b97b0b7568b8a358191188f20ec' 
  AND token = 'l3GwM3yI6veEBig1ybxzCUdqNB+wIglelVScBMPpers=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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