SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '7f278aa5ab38b507c21769920cab1b92c75e203e73052731e1d488a075ee642f' 
  AND token = 'Gngla93eA+YjnBSTmXzrojIJWiImRZbbudE76ubCGzY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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