SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd6feffce8f5e0a12752537d04a553d2ef807620130d278684addd9b683d3ab2a' 
  AND token = 'F0xgOFMdXJEngkEXcaYkQ4uQl0W1rL1CDvUwSfEOuBM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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