SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6e173d6e77c88d927e068440f0ad9b3f29bf2c78de28fb73b27a9acfdff86855' 
  AND token = 'S2lHhqEtntPAteWUzrPFBd38rF/kAfPZrWXfktMfCR4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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