SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '83543d41fbe1340fae382e28babed1a09b99a13e6d082099d68ffc1d182d4f9f' 
  AND token = 'QaZ7T1xtvVoDDvsV6rOxncoUsgqjki+bT8+KMzeHyEg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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