SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8fff1ab15e1782b1c73017afdfc4ff0410a2e77f5bc1de86033b46d93b949068' 
  AND token = 'jnpt//U1EOCeWVNRUcscvLkug0SsSwlXM1e2URCpxxY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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