SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'df0ecadad2f1d7cb5d12e58075be5f816956ec984fe889b35718c4985544021b' 
  AND token = 'oUst8l259DAzg2NcPfTWdNaXZIwRok1baXf9STR+hhE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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