SELECT 
  1 
FROM 
  cscart_aprillock_keys 
WHERE 
  key_id = '51ea3e4d2313ce7cbd80dc7802151b49cc969788ed94f60548c8adf7a498d081' 
  AND token = 'PhXPhB8oQyiTQgqndiRXYdLhgPhGIysTKKJdDKYKd+k=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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