SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b8f565870576c17de8d3c18257ea581364e49622e48f365effd50f470c355123' 
  AND token = 'PvIrTCw1mVMWbzEsGCSR3VpIFxyt/jTI2RrDWBshDDo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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