SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b6336092823508c2cb55c50776a90d554f8b6255b64b4cade1133f0ece845c8a' 
  AND token = 'CiMMs0wdUdmH/ejPyGMTShMXs6FC7GzVydUswYqmf7I=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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