SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b4b63991053b24cb3fcdfce3a97788993f613467028de038af629a99b4dbf1eb' 
  AND token = '+sZ8EZ1S4PSHKejPLfKZFLlGtI5vPrOOXaqNNaFv6LM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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