SELECT 
  1 
FROM 
  cscart_aprillock_keys 
WHERE 
  key_id = '51ff30bf4f6e08435a3000f2e562b0816584c10c1965a8db237e1f9a6eef883a' 
  AND token = '53OqgqVLjJTR9bK928JBKsU2tZgcYO7kBLhKVCdttaE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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