SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '55daf81e760c4dd3785b961ed159b208bff67441c13aec2950f4e68052c7b4d2' 
  AND token = 'OQM56fB0mmXSaY3LRDgNaEUzCGkv1UQHVFkTajwTJt8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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