SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b4fcb1618fc2f13bdf11fc4d1407d32a17aa4fbcce5ce8e85a7b029964847d74' 
  AND token = 'ID/OySsbmLxwWwtc3fQKiwo3GMyE0mJckTylPeD1tUY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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