SELECT 
  1 
FROM 
  cscart_aprillock_keys 
WHERE 
  key_id = 'ec75f7b545850fa4760a0a7fc69fa26070b3b31e30c3f396edc29cc1b8a97b55' 
  AND token = '5iB0JgrvJ1Ki/ZxYC0X+z0VOg5uzOXRNy0E5DGS8NDI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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