SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '75844583ea1a949ad30b99b2f395e4cabe75a864f1022e69946591dd177843d8' 
  AND token = 'EKecYdgCNipSPeniRcQXw1tyLqWZjy72cTSspmqTrWI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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