SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b51ecea2191f2c7dd768c7a35b5d073e20dce8aba682feeea0f8867cb05b611e' 
  AND token = 'os8A435d0s54DvutzC8riHqThYsvbjkdMnmz16X7IJU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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