SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b39f5265f22f682959f328c02e3b3caa29b084c612fbf5997bc8a0f61b405144' 
  AND token = 'zqJXn2o5R7ddhHUMU2dGEmzQqfdiiIaFhpKHYBua+DA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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