SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c50cc5d247ffdb6131d0088447778ddd0046c6d9853dea689e326cca928fa1c1' 
  AND token = 'hTIfQJoK7fg+czw8Nbc3b61LkIfRLlbcc3urnABppzQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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