SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b4d4895d0a843aad8d8e142aaad2aefeb055eb9a9ebe6624a6373c9d326b9fbc' 
  AND token = 'z3K/W0Q9HL7iqY9SZwpXaAV9AkBLmOPKGVslgNfIQEk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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